A few decades ago, clothing stores
used to sell these. This was just like an ordinary suit except it came with two identical pairs of matching pants instead of one. Of course, if you bought one of these you might be upset if you got an ugly irremovable stain
on the jacket. Mostly though, pants wear out or get damaged more often for some reason people tend to sit on them
so these were a naturally popular product.
I suppose people must have just gotten tired of them. After all, a conspiracy to sell more complete suits by eliminating them would be very hard to hold together. Any manufacturer or store offering them would draw consumers away from competitors. If someone was destroying people who violated the cartel, we would know, wouldn't we?
Unless it was the Illuminati or Freemasons or someone like that.