I know what you mean, about people rebelling against authority or their parents. I was raised by my grandparents, they always wanted me to dress like a prep. I really hated it because, that wasn't who I was. So I changed how I looked. I guess you could say it was kind of out of rebellion. But, I didn't do it solely because I wanted to "get back at them". It just didn't make me comfortable, I wasn't comfortable in my own skin when I wore clothes like that.
For some people that act out in certain ways, they feel the only closure is to be "different" they will join a specific group of people, or do certain things to be accepted because they feel rejected by some one. If a parent wants them to be a certain way, or dress a certain way, but they want to wear something else. Then, they will act out and do something "crazy".
Sometimes people get into the wrong crowd, and the crowd can influence what some one does to themselves. Sometimes something big happens in someones life and they feel they can only relieve the pain by cutting themselves, or wearing all black, because it gives the feeling of closure. It's hard to understand why some people do the things they do. There is usually something that happened in that persons life to make them change drastically and to rebel against certain authority.
I don't like scene kids, allot of them are posers, (sorry) it just feels that way. But anyways, some people just feel it's right for them, whatever it is. Some people get the pleasure of wearing cardigan sweaters and going to a coffee shop every afternoon because it makes them feel comfortable, others will wear jet black parachute pants and wear black makeup or something and cut themselves, because it gives them closure and makes them feel comfortable.
Like I said before there is just sometimes something happens in someones life that makes them choose the path that they go. I bet If you sit someone down and asked them, they might tell you. Sometimes, that's all that people need, someone to talk to.