Subcultures can divide people

From what I understand, subcultures are there because they allow for people of certain characteristics - whether they're fringe or simply uncommon among the general population enough to not be seen as "normal" - to feel appreciated, to belong with others like them. They give what others failed to - the idea that those people aren't foreign or alien, that they are "normal" in their own way, which is very important for people who didn't feel like they're among the right crowd (the right crowd for them, that is) for long enough. Subcultures are just bigger, more prominent or publicly-known groups like this.

If the ideology within the person in a group is strong enough or if the person prefers to stay in their crafted bubble instead of facing the world, they'd rather isolate themselves rather than be open to all experiences - which, interestingly enough, unbounds them from the labels their preferred (or, seemingly preferred) companies might lay upon them. Your crowd defines you as much as you define your crowd. You might be partly a goth, but if you also climb mountains, play some exotic musical instrument and write meaningful replies in one of those online forums, you're not defined by being a goth - nor have you allowed yourself to be so. I guess this is how you don't fall into those nasty isolationist traps: by belonging to what defines you best, and crafting your own if what world gives you is not enough.