As Ratant notes... For a while, there was a very strong rehabilitation program in effect in prisons all across the country. Education, skills training, etc.
For the most part, this is by the boards now. The factors cited are:
1. Cost
2. "Coddling" criminals.
As also noted, no politician wants to be seen as "soft on crime".
Unfortunately, as I maintain in other areas of social justice, you are going to have to pay one way or the other.
We arrest the same people over and over again. Our neighboring department just arrested a fellow burglarizing apartments. He had been out of jail for two weeks. He not only promptly went back into crime, he went back into the very same neighborhood he'd been burglarizing before.
At the university, we have suspects who are so familiar to us that a description of the crime will give us a list of suspects immediately. In for a couple of years (typical sentences for petty theft) and then out... No job, no training, no chance of getting anything other than the most menial minimum-wage job... Little wonder these folks go back into crime.
We are creating a permanent underclass of people with no skills save criminal skills, no prospects, and who in many cases have spent half their lives incarcerated.
We have, we understand, about a million people in jail/prison at any particular time. That's a constantly-rotating population, of course. Recidivism runs 40-60% depending on the type of crime.