Several times last summer I joined a huge group ride that takes place every week in Salt Lake City. Most of the participants are in the 18-30 year old middle class demographic, and I believe many are students at the University of Utah. There's high female participation, close to 50%. The emphasis is not on serious riding or on the bikes themselves--it's more like a big party on wheels, with lots of alcohol being consumed and various substances being smoked.

When I say this ride is huge, I mean we sometimes had upwards of 400 riders.

A casual observation revealed that these folks ride a tremendously diverse collection of bikes. Vintage 2x10 road bikes, coaster brake beach cruisers, crappy department store mountain bikes, fat tire e-bikes, and many other types are represented in plentiful numbers. There are also quite a few single speed and fixed gear... I'd say perhaps as high as 10 or 15%. There's a few really nice track bikes, but not many. Ditto high-end city/commuter/touring bikes. And even fewer modern carbon fiber road (race) bikes.

I don't know how the fixie culture looked around here 3, 5, or 10 years ago. Currently it appears to be extant--if not particularly strong--based on what I saw in that group.