I can think of a few more reasons too: 1) Rehabilitation and its benefits can't be as simply explained. In politics, where the other side will be scrutinising

I can think of a few more reasons too: 1) Rehabilitation and its benefits can't be as simply explained. In politics, where the other side will be scrutinising your every word for something they can twist out of context, simple = good. You want a simple message and you want to repeat it endlessly. 2) There are powerful interests that benefit from the current prison system - private prison operators and prison guard unions to name two. 3) Rehabilitation won't always work. If you endorse it, and even one prisoner gets out and rapes/murders someone your opponents will drag your name (and career) through the mud. "Person X would still be alive today if not for Candidate Y!" sort of things.