Well loads of people do that because either they are "depressed", or for some reason it makes them "different". Well one question is how does cutting yourself help you? If you feel emotional pain, how does physical pain help you? And I guess cutting yourself makes you look different because you make yourself look crazy with all those scars!
As for if someone's done this at my school, yes. There was some girl who was cutting herself in class and then ended up needing to go to the hospital. later that same week, she was caught making out with a girl. So I guess if you cut yourself then you can get girls XD