A lot of "bad people" succeed in the outside in politics, banking, venture capital, and frankly every industry. A lot of "bad people" in prison could easily be leading much different lives if they were born into different circumstances. How do you expect these people to become productive members of society and transition from "bad people" to useful citizens if you deny them any help or any tools to do so? If your only choice for survival is to sell drugs, then you're probably going to sell drugs. If there are better options, most people will take them.