What Good does Prison do?

Rehab lets them live a life while getting Help, no?
They can work, visit family, ect.
Jail's policy has you in there for so long and, unless you misbehave, you get out at the end of that time. Therapy isn't based on the time you stay in it, it's based on how you deal with it. You get out when you're ready, not when the calender says a certain number.

Not all rehab's are like that. Then again, not all jails are like that either. In jail they are allowed to get an education, work (if they are a certain level within the jail), visit with friends and family on designated days. Jail also has therapists that help the prisoners with their issues. Not saying it works, but it's there.

Some rehab's don't allow you to work, have visitors, get an education.