For some people prison is a real deterrent.
I knew someone who got sent away, for an offence greater than the one she'd actually committed. The sentence was one year, plus 6 months to run concurrently (at the same time). At the 3 months point, she was released on tag - she has to remain indoors between 6:45pm and 6:45am - for another 3 months. She likens this to being in prison again - locked up for 12 hours a day. If she sets one foot wrong, she will get recalled to prison again, and she has this hanging over her every day - it terrifies her. She has no intention of seeing the people she used to hang around with - prison has certainly worked for her.
The thing she hated most about prison is being so far from home - she was moved to drake hall in eccleshall for 2 months of her sentence. We still went to visit though - it was 107 miles away. For one month she was in new hall, wakefield, alongside murderers and peado's. All she did was punch someone in the face a couple of times
Of course, then there's those for whom prison is a part of life. For these there should be two classes of prison - normal prison as we see today, and a more strict, higher-class prison, where prisoners dont have a choice of food, dont have 12 hours a day to socialise, and have less visiting rights (and be further from home!)