>>1967952many reasons but here's a few
1. they're often badly set up (bad fit, wrong size) because they are pitched to noobs and people on a strict budget, this would be less of a concern for riding that didn't put such high stress on various joints but fixed gear does
2. grinding your way out of every problem is hell on the knees, it's one thing to do 3 sets of 15 in the gym and then you're done but over and over and over again grinds away at cartilage in ways that won't be evident until it's too late
3. extremely terrible, dangerous unnecessary nonsense like using toe straps instead of clipless, and riding brakeless, and stuff like that, since fixed gear culture positions itself as a "counterculture" any attempt to talk reason into the cultists is met with hostility
like most bad decisions most of it is not bad in the abstract but it's bad as applied in practice and that boils down to bad. whatever wisdom would talk the average fixietard out of doing something stupid would be delivered to his brain in such a way that he would realize the whole thing is dumb, so you're never really going to see, for instance, a fixietard with a correctly sized frame and correct stem and bars and correct crank length and so on, once they've got that shit sorted they've almost certainly realized that the fixie part is also a big mistake
