The biggest issue is that 95% of them will be returned within a few months. Drugs is the main cause. You get out, you have no ID, no job, no family, no friends. You're stuck in a halfway house that is just like being in prison (lots of rules, line up for meal service etc). All the other guys there have a ton of drugs and you swear you won't touch them, but then you do because you're bored and sad. And then you're addicted again. And now you need money to buy more drugs. So you go do something goofy to get money and you get caught and locked up for another 10 piece. Or your parole officer drug tests you and violates your parole and you go do another 3 piece. Or the halfway house owner gets sick of you coming in after 7pm smelling of alcohol so he calls your parole officer and you go do another 3 piece.
Cycle repeats until you die in prison.