From my perspective, I've found that many against promoting rehabilitation (at least for less heinous crimes) tend to see prison as a day at the park. Essentia

From my perspective, I've found that many against promoting rehabilitation (at least for less heinous crimes) tend to see prison as a day at the park. Essentially, they're trapped in a prison in the form of low income or poverty where significant portions of their time must be spent working. They don't understand how a prisoner could potentially or at least perceptually be better off than them: consistent housing provided, guaranteed food, medical treatment, time for education and growth. When you have such gaps with economic inequality in a society where for those on the lower end of the spectrum combined with some misconception of prison life, prison can actually seem better, you have many who tend to promote punishment over rehabilitation. "Someone did something society deemed as negative and they're rewarded, I did what society said was positive and seem to be punished relative to those acted negatively. I struggle to survive and work constantly while this person leisures (albeit with limited freedom) and studies." So as you coined it, probably spite.