Say you're the kid left at mom's boyfriend's place. Who's gonna take you in and be your role model? The kid with a knife, who will teach you to mug people on their doorsteps.
Alternatively, we could take funding from the admittedly ineffective police, and put those resources into service work. Fund support structures, and provide better role models to the neighborhoods that need them so badly. They're probably there already, but they keep their heads down and act tough when needed, because that's a survival tactic.
It's not that people want to live a life of crime, but when it's all you've ever known, it's nigh impossible to break that cycle on their own.