Why do young girls enjoy dating bad boys?

OK, so my question is...Why do Girls like dating bad boys. I mean, I understand u girls like a guy who is not predictable & easy & u want a challenge, but is it really worth the sorrow of displeasure in the long run? Personally I do feel like I am one of those good guys but likes a challenge & wants 2 be with a girl who knows wut she wants. See the thing is I like this girl and in my eyes she is pretty, What is the best method to take if you like a girl who has low self esteem about herself, is it worth trying to change her? I mean she does like me so thats good and she wants reurance from me, but I cannot believe how much her ex b/f broke her down mentally with his stupid ways, & personally wen girls say its a challenge or they wanna confident guy. To be honest with u guys, I have met Michael Jordan at his bball camp, yet I always heard he was a jerk on the court because he had desire to win and knew what he wanted, but off the court, seriously one of the most genuine ppl out there