Prison does NOT work. I have worked inside a prison. Over 75% of people sentenced to even a very short time in prison NEVER get a paid job again. This is due to the bias against employing an 'ex con'. So most of them end up offending again just to get money. That means they often get sent back to prison time after time.
A suspended sentence means that if you get arrested or break any of the conditions of the suspension you can go straight into prison without another trial. It also shows as a prison sentence on your criminal record. So a suspended sentence is a major deterrent and almost certainly does more good than locking someone up.
Jourdain, Community service , unpaid work for the good of the community is a good alternative to prison. Another reason for avoiding prison if possible is that is is VERY expensive.
The UK spent £3 Billion on prisons in 2016 ( the last year for which figures are available. Or £38,000 per prisoner a year
http://www.russellwebster.com/prisoncosts17/