Having lived that life for quite some time, it's really just like @[HP] and @Minos describe. If you live among the poor, the unwanted, the criminals, dealers and junkies, it's not really a choice. It's not that a life of crime or easy money is more appealing, for many that's all there is. People know who you are and who you associate with. They don't give you chances. The government doesn't give you chances. They keep you in that environment and out there, only the strong and ruthless survive. The weak and poor are always being fucked over by the rich. Always have, always will.
I was lucky because I met a uptown girl who had a weak spot for bad boys. The girl wasn't that interesting, but her parents really fell in love with me. They took me in. Cleaned me up, arranged an education, job and what not. They gave me a chance to escape that life. Without them, I would have been another lost soul.