Exactly. It's easier to let convicted criminals out than to come up with a solution to the overcrowded prisons.
Why not just build more prisons? And invest in rehabilitation to cut down on re-offending rather than locking people up for 23 hours a day.
Because prisons aren't shown to be much of a deterrent and leads to a high percentage of reoffending. In some cases prisons are basically seen as criminal gang recruitment centres.
People who get drawn further and further into that world for what started out as minor offences. Things like drugs, swift changes in circumstances (especially economic like job loss), family/socio-economic problems. People that can be helped but end up in a much worse position because they've been sent to prison.
Meanwhile other countries in Scandinavia concentrate almost wholly on rehabilitation with a tiny prison population and all the indicators are that it's far more successful. In fact they say the biggest problem is people like you moaning why criminals aren't being punished.
For me prison should be there purely for those who pose a physical threat to people, and would happily say for some of them to even be considered for release after extensive rehabilitation they have to wear a tag for the rest of their lives.
So ask yourself are you interesting in solving the amount of crime and the reasons for it, or just punishment?