1. If you go to prison, innocent or otherwise, you're not getting hired afterward. This leads to desperation, desperation leads to...
2. In prison, you become socially reliant on criminals to simply get by. This results in cultural transference. Someone getting in trouble for shoplifting learns about the joys of [insert more lucrative criminal activity here]. Combine this with point 1 and you get repeat offenders who become 'hardened' criminals. Basically, they get better at crime, because crime involves skills just like everything else in life.
3. Poor prison conditions result in psychological trauma. This, in turn, leads to anti-social behavior.
In short, we pay a lot of money to create better criminals who are highly motivated to commit more crimes.
Recidivism is very high when people get PTSD, no mental health support or any support whatsoever when they are let free after a decade or two. In civilised countries the prison systems main objective is preparing someone for the life after prison. In other countries revenge is the top priority
People go in for minor crimes, get mixed up with gangs with hardened criminals and learn the trade. Once outside they have no opportunities so they become a hardened criminal. The system just sucks.
