Yes, it does seem like a weakness to see people mindlessly adopting the same things as other people. There must be an evolutionary advantage to it, though. It probably increases bonding between people. Fashions are like uniforms. It's a way of signalling to people that you're part of their group. It shows that you're keen to fit in, even if it makes you look daft or walk funny.

Some people really do have a problem if you tell them you don't drink alcohol, though. It's as if your decision to opt out is somehow a threat to their way of enjoying themselves. It's probably because they secretly fear that they should not be relying on alcohol to have fun.