"Have you ever really _looked_ in a clothing store? There is a tremendous degree of variety available, especially for women."
Not really. What there is for women and men is an-ever morphing "look," which, with a few minor variations, is pretty uniform. That's why you can "date" a look/fashion for any five year period. For example, for the last six years or so, the "look" in bathing suits is either racer one piece suits or bikinis with high cut bottoms (makes the legs look long and comes way up on the hips). I am intimately aquainted with this look because it doesn't suit my body; therefore, I have not been able to buy a bikini in a long time and have taken to making my own. That's not what I would call a free market. Look at shoes: the current look right now is either that medieval looking stuff with long pointy toes, or a square cut duck-bill look. I hate both, so I'm not buying shoes.
While it's true that you can sew your own, frequent used clothing shops, etc, that has always been the case. But, in fact, most people would rather "look like everyone else" and purchase ready made "fashionable" clothing.
Of course, there is always a "collective unconscious" that influences fashion, which explains the jeans and army garb of the sixties, the bag lady look of the late seventies and early eighties, and the hip-hop look of the nineties. This is more like "fashion" from below, which is quickly captured and reproduced by the fashion industry.
Joanna