I think it's a question of perceived virility. Bad Boys aren't afraid to show off and be "manly", which seems to feed into the hormonal racial survival twaddle about picking out the so-called "most potent" of the gene pool.
Interestingly enough, studies have brought up the point that once the female becomes pregnant, she will seek out the Nice Guy as nurturer and provider for her offspring. Taking this a step further (though I doubt the validity of this claim), women want more "sensitive" men now because of the last two generations of women having been exposed to birth control, which kicks in the "seek nurturer" trait due to the hormones making the body think it's pregnant. I am of the inclination that the research money was embezzled.
However, there may also be a play of psychology here, as most of the "Bad Boys" I see around my area are also abusive losers who cheat, beat, and are passive-aggressive children. They also get laid more often, judging by the amount of women they get pregnant. The women who chose them seem to have low esteem, low standards, and the inability to figure out how to use birth control, with the excuse of "The is the best we've got, and he's good in the sack." Which, of course, validates my theory of perceived virility being that the women won't give the Nice Guys the time of day to practice being better. The cycle perpetuates itself.
Admittedly, my idea of a Bad Boy is having a perceived virility just under the surface of respectability and manners, which means he's a demanding Dom in private.