The 10" single still gets a lot of respect among indie kids, for at least three reasons:
The 10" bridges the uncomfortable gap between the 7" and the 12". On all vinyl, there's a trade-off made between running time and sound quality: using 33rpm and a tightly wound groove lets you fit an album's worth of material onto a 12", or an EP onto a 7", but at the expense of sound quality and susceptability to dust and scratches. Using 45rpm and a loosely wound groove, a 7" can hold a reasonable quality single, and a 12" single gets fantastic sound reproduction.
The 12" single's quality and expense is excessive for many subjects, particularly shorter songs which wouldn't see any benefit from the extra elbow room on a 12" blank. This is where the 10" format steps in: a significantly smaller disc with sound quality indistinguishable from the equivalent 12".
A popular format for 10's is as a 3-track EP with a high-quality A-side, and 2 tracks of slightly lower quality on the B-side; a good trade-off which gives the record buying public the song they wanted at high quality, but also gives a better oportunity to strut your stuff and demonstrate your range than is afforded by the single B-side (or 2 crap-sounding b-sides) on a 7".
Since it's one of the older formats, there's a quaint historical appeal, and a nod of the head to those who came before.
Possibly the most important of the three, and highly prized by us indie kids. The fact is that there just aren't as many of them around as there are 7"s or 12"s. So, naturally, they must be cooler, QED.
Also, they're excitingly chunky. 12"s are just large enough to be awkward to handle; 7"s are easy to maneouver, but feel insubstantial in the hand. A 10" feels... just right.
That's not innuendo, by the way.