It's the culture behind it, or at least mainstream rap, that basically in order to be cool and successful you have to be 'gangsta', eg: crime, have sex with every fit women you see, etc. For example my friend has recently tried to get in with some 'gangstas' and being the impressionable idiot he is taken up smoking, been beaten up twice and is even more obsessed with sex than he already is, at the point where he has said in the space of a few months that he is in love with fit girl after fit girl. But that could just be the people and not necessarily the music.