It may sound like utter rubbish to you, but it is factual results from the US.
Are you seriously asking that question Josephine how do you punish people without the threat of jail?
The majority of people need rehabilitation, surely we want to utilise and involve society as a whole. People don't generally steal a car because they just cant help themselves and must be kept under lock and key in order to prevent them from doing so. Usually, poverty, unemployment (and therefore poverty), drugs, lack of education lead them to make such choices.
As a society we have to invest in people, particularly when they tend to be individuals the state has failed (considering how many of the UK prison population comes form a care background). In the Uk roughly 2 out of 3 prisoners re-offend.
Also around 70% or male and female prisoners have 2 or more mental disorders, over half have drug problem prior to entering prison and around half have alcohol problems, similarly around half were expelled from school. Most convicts come from systemically dysfunctional backgrounds, to just house them and wait for them to do it again fails them and us as a society.