The problem is that you can't return an unrehabilitated criminal into society and expect good citizenship from him; an unrehabilitated criminal is still a criminal. He will commit more crimes.
Our justice system is fundamentally flawed because it achieves none of the purposes of criminal justice, which are:
1. Punishment. Our system doesn't really punish; it coddles them in confinement.
2. Restitution. There is very little effort to make criminals pay back the victim for his loss.
3. Deterrence. Our prisons are often more comfortable (emotionally and physically) for the criminals than the environment in which they live. They aren't deterred by our "punishment." They mock it.
4. Rehabilitation. They might get counseling. They might get a lecture and a wagging finger, but they don't change.
A man who steals ought to be whipped. Then he ought to be made to pay back the victim, plus a penalty. If he can't pay it, he'll have to work it off -- put him under the authority and command of the victim until he makes it right.
A man who molests a child ought to be executed. He's not fit to live, and it's not worth the effort to rehabilitate him. Same for rapists, kidnappers, and murderers.
Our current system is totally inhumane. It places human beings in cages, gives them comforts in confinement (like rats), and does nothing to restore them to usefulness, productivity, and moral worth. It just churns them back out into society without fixing their problem, all while claiming to be more "humane" than a whipping. It's absurd. No, it's not merely absurd. It's frankly wicked.