now I gave this a lot of thought and I think I actually have a reasonable answer!
I think "good" girls like "bad" boys because "bad" boys are generally doing something that they (the girl) have never done. (in a gang, smoking weed, stealing, ect.) and when a guy can educate you on something it's a turn on. My brothers roomates smoke weed and I was asking all kinds of stuff about it and something about it just intrigued me (no, I didnt smoke it)...I wasnt attracted to them but the fact that they were telling me things that I dont know made me very interested in being around them. I just think girls get interested and when they start getting educated they form a liking for the person because they have taught them something that noone ever has before...or from a different perspective. Ya know?
I hope that made as much since to you as it did in my head lol
"An it harm none, do what ye will."