Cyberpunk, which is now extraordinarily quaint, was the product of 1980s science fiction speculating a dystopian future viewed from a society's underclass. Whereas 1940s and 1960s sci-fi mostly championed the idea of a brave new world where humanity sheds its internal strife and marches in unison across the stars (Star Trek is literally Wagon Train in space) with pretty, breast-enhancing clothing and beehive hairdos - the 1980s envisaged a world where gene splicing and nanotechnology wouldn't be used to cure cancer and solve the energy crisis or whatever, but be used to implant vat-grown muscle, do street "body adornment" or help us kill or get high.
The Cyberpunk aesthetic drove a lot of 80s movies (Blade Runner, and to a lesser extent The Terminator) and a lot of 1990s culture (Aliens, Red Dwarf. The look is now quaintly dated, dark industrial metal and grainy green CRT screens - whereas getting close to the actual 2020 that a lot of it was speculating about - we're more about brushed aluminum and flat screen. Of course, any futuristic movie is going to look dated soon - you don't have to look back at 1950s Buck Rogers with sparking cigar-shaped "rockets" or arcing high-voltage coils and nixie displays - just look at the quaint 60s vibrancy of Star Trek. We're not so much about factory floor of Weyland-Yutani, and few people are sporting implanted computers. But the "punk" part of Cyberpunk was about it being about what the street, especially the lowlives chose to do with new technology. For the record, "cyber" comes from the Greek κυβερνάω (kyberno) which means "to pilot, or steer".
Quick on to follow was splatterpunk, a horror subgenre which was in essence the Saw movie franchise in print. No prizes for guessing what the splatter comes from, it's really what it says on the tin. Clive Barker wrote a compelling short novella called "The Hellbound Heart" about a man who opens a portal to hell and escapes flesh-rending hooks and endless torture to regrow, like a wax statue melting in reverse, consuming the blood and life essence of men his brother's wife brings home for him to feed on. It went on to become Hellraiser in the theater, and if blood and gore sold, the splatter folks upped it to 11.
But then the two men who were leading lights in the Cyberpunk scene decided to do something intriguing. Turning to speculative fiction they wrote a book called The Difference Engine which posited that Babbage had actually built a working Engine and that the computer revolution had happened in the Victorian Era. Whereas Cyberpunk was about computer chips and Tokyo and megahertz in electronics, what then became known as steampunk imagined a world where we were into gear-inches and so forth, deriving computing power from gear-driven clockwork and telecommunications from punched tape leaving a telegraph. The Victorian era was famous for a lot of things, including its London underbelly - and William Gibson and Bruce Sterilng enjoyed tremendously writing a kind of murderous noir about ripped up prostitutes, card sharps and various east end lowlives. The steam part came from the notion that these engines would be steam-driven, just as all trains and heavy machinery were.
Cyberpunk quickly devolved from quirky DIY punk movement into fashion statement - the first people hacked their brains with nutrients or Russian smart drugs, built their own quirky wearable tech or otherwise looked to repurpose things from Radio Shack and Fry's - but soon it was about mirrorshades, black jeans, black boots and a long black leather trenchcoat while listening to Wumpscut. Also predictably, it turned into some young women gluing microchips to their naked bodies and doing photo shoots saying "look at my tits!" So by the time steampunk happened, the fast-track to people wearing brass-framed welding goggles and dressing like either The Mad Hatter or some over-fripperied Victorian dame came pretty fast. Nobody really wanted to ever replace their Blackberry with something made of brass clockwork- in fact the reason Babbage didn't create a working Engine is that it took modern techniques and computer-guided machining to make cogs and gears to the tolerances Babbage would have required to make the Engine work. (It worked in theory, but could not by their technology be made to work in practice.)
Historical accuracy be damned with Steampunk, anyway. Nobody sought to wear what people in the Victorian era would actually have worn, but instead created a look "inspired by" the Victorian era - keeping the cloth and the best of BBC drama costume porn but having it be a lot more revealing and pairing it with tattoos and showing a level of skin that the Victorians would have never tolerated, e.g. ankles. The Victorian era was about taste, and the notion of walking in covered in brass accoutrements, showing off your thighs and wearing what amounted to a society ball gown edited down to swimsuit coverage would not have sat well withe marms of the day. But in a world with mundane objects that at the time were "computer beige" (now "computer brushed aluminum") the notion of something with ornamentation and made for aesthetics as much as for use was a real draw - and people made computer cases with nonfunctioning brass gears and repurposed old Underwood typewriters to make brass, oiled wood and typewriter key keyboards. The tragedy of this butchering is to have resulted in the destruction of thousands of genuine artifacts from the early 20th century as things were gutted for clockwork and keys, leading to the driving up in price of anything containing either. Intriguingly, the steampunkers got what the Victorians wanted to have happen done right - Oscar Wilde bemoaned that rather than having ONE or TWO ornamented pieces, what people tended to do was gather everything in the house with clashing scrollwork, ornament and frippery, leading to a cacophony of dissonant styling. By having few, bespoke items with a tasteful amount of ornament, they managed to nail how Victorian styling was supposed to go.
Right on the heels of that came dieselpunk, which centered around the early to mid 20th century, in essence taking Americana and hot rod culture and putting it on steroids. The Rocketeer imagined a 1940s with brass-framed jetpacks and Art Deco styling. Who really could argue with a dapperer time in which men used pomade and hair tonic and were never fully dressed without a hat? The -punk part got kept as well. Sure, finger waves and gingham skirts, but they weren't quite as conservative or old-lady frumpy as what the Golden Girls would have rocked, and of course, the tattoos and piercings, right?
There's now a -punk for everything. There's even clockpunk, which proposes a pre-Victorian, Georgian speculative era with hand-wound clock computers and being dressed like people in Black Adder the Third. If you ever wanted to dress like you were in the Revolutionary War, and of course pair that with showing off your breasts, that's an option.
Funny thing is, whenever people wish they'd lived in the past, chances are they're only looking for part of that experience. The dark joke one guy made (and it was used in Doctor Who) was that time travel is only fun if you're rich, if you're healthy, and if you're white. When people express a desire to have lived in the Victorian Era, they were thinking about being nobility or the wealthy class living in beautiful neo-Gothic architecture, not an orphan dying of syphilis at 15 in a back alley near Carnaby Street or choking out his last at 9 stuck in a chimney. When they imagine the fun of being in the 1940s, it's not getting tortured in a Japanese POW camp or being lynched for being black in Mississippi. It's a selective picking and choosing, and the "speculative" part is all about wanting the good from the modern (Google, dentistry, etc.) with less of the "disposable culture" as in generations past.
Truth be told, though - it's technically possible for any of us to regenerate or repurpose artifacts from bygone eras. Men shave with straight razors bought off eBay that were found in grand-dad's desk drawer. Hot rodders find old cars and rebuild them- sometimes to gleaming original, but sometimes to crudely stenciled skulls and no mufflers in a genre called rat rodding. Women can buy any kind of clothing, from replica hoop skirts and corsets to imagined dystopian futuristic futiques. Maker faires allow people to work in brass, in copper, bend tubing, rediscover older technologies - sometimes built better because of newer techniques. If you want to live in an imagined 1970s, Dodge makes the Challenger which would pass on the outside for a 70s muscle car, and Fuzz Dandy makes bell bottoms that wouldn't seem out of place in That 70s Show. 1950s? Any of a number of places. Heck, poodle skirts are practically a Hallowe'en staple, and parents think nothing of dressing up their 5 year olds like The Fonz, even though at the time that would be considered child abuse. (The quaint movie Cry Baby shows two children extracted from a house in part because the kids dress like drapes).
What started out as an attempt to DIY an older technology turned into a way to buy into an older aesthetic and/or live on it via etsy. We're in a brave new world where if you want to live by past looks, past technolgies, past aesthetics, or even past ethics, it can be done. Heck, there's even Amish porn.