I despise it when people use the term rehabilitation with regards to criminals. They are not generally sick or disabled people. They are individuals who have made choices about their lives and others. True, criminals can reform, but it is up to them to demonstrate that they have done so. We should be seeking out the best and the brightest of the criminal population and rewarding their behavior with cushy white collar jobs.
I've talked with a couple parole officers and they say the same thing. The people they deal with really have to decide for themselves to change, it isn't a matter of changing their environment.