In modern prisons, prisoners spend their time exercising and getting degrees (at least according to films). Maybe imprisonment wouldn't be such a drag if there was an opportunity for prisoners to increase their skills at a faster rate than they normally could. So every hour they spend studying or training in prison is like 2 or 3 hours on the outside. By the time they get out they could have mad swordfighting skills, and it's less boring for the player.
