The thing is, prisons are *supposed* to rehabilitate people. A lot of people think prisons exist for punishment, but punishment is only an effective way of teaching people not to get caught. Some people think prisons are simply to keep dangerous people off the streets, but if that's the case then they should all be killed (I don't believe that, obviously, but it's the logical followup to keeping people off the streets).
By the sounds of this, and stories I've heard from my uncle (who's a prison guard) and other places, it sounds like prisons make no attempt whatsoever to rehabilitate. In fact, the people who come out seem worse off than when they went in, and *more* likely to commit a violent crime or hurt people. That's an epic failure of the prison system, IMO.