The purpose of prison is punishment and serving justice, not trying to rehab or any of that. The problem with prison now is that there is no emphasis on making the prisons safe for prisoners to serve out their time. And really no one cares about that because, after all, they are criminals. I think there should be stratification based on severity of the crime they are convicted of. Murderers get housed seperate from rapists who are seperate from robbers who are seperate from white collar, etc.
That way the kid who is serving a mandatory minimum for slinging weed is not fucked with by the guy who raped and murdered someone.