My father was a sheriff and handled the prisons for our county. (Ironically, my grandfather was a felon for robbing a bank) Here's my 2.5 cents. We don't have more criminals than other nations, actually we're quite low in the number of offenses. But we do have mandatory sentencing and very long prison terms, so we have more criminals in the system. Every holiday, Thanksgiving for example, there would be 2 or 3 convicts invited to our house to have a good meal and a chance for a break from the prison grind. Usually the guys committed property or other non violent crime, but sometimes assault and battery. While in most other nations these criminals would server sentences ranging from 6-20 months, and was the case in the US decades ago, in our system today they now serve 3-5 years.
So you've got some dude that, for whatever reason, decided to rob a house or steal from a liquor store. He gets caught, you always do eventually, and end up in jail. He probably feels bad and remorseful, even if only because he got caught. Either way, you'll end up spending a decent chunk of time in the slammer that usually costs you your job and maybe even your family. Hence why my old man liked to bring these guys around. It wasn't charity. He'd invite them, they could turn him down or not. Nor were they expected to 'work it off' as so many people seem to think when I tell them this story.
Other things he did before mandatory sentencing became overbearing were;
1) Weekend prison stays for non-violent and first time offenders. There was an honor system involved in this. The idea being if you were truly sorry you'd do the time and be thankful you still had a job on the weekdays.
2) Work release programs where local businesses would hire prisoners for odds and ends. They got paid immediately, perhaps it was low I do not know, but it was real money that lots of guys gave to their families who needed it now that the bread winner was in the slammer.
3) Mock chain gangs. Prisoners who wanted a chance to leave the walls could dress up in the joke outfits and go around place to place singing stupid songs about prison life. Shools, malls, places like that.
4) A slew of other options for men to do their time with dignity. Decades ago, it was thought that surrounding normally decent people with true thugs was not such a good idea.
What happened in the last couple of decades was the use of metrics and statistics. Politicians could go out and say things like, "vote for me and I'll keep the prisoners in jail longer. Look at what [insert State here] did! They upped minimum sentences and now property theft is down 20%". Sounds good to a voter I suppose, however it's really kind of useless since it discounts better law enforcement and education in the first place, not to mention the dramatic increase in repeat offenses. The solution... "Longer prison terms for repeat offenders!" Now you rob a store that is occupied and it's jail for 15 years. You get caught with drugs 'next' (within 3 miles) of a school and you get tossed in the big house for 6 years. Good luck trying to not live withing 6 miles of a school, or robbing a store with people in it. I'm not trying to put on a liberal sob story, but from my very conservative point of view and upbringing things have dramatically changed. It's almost as if you've got nothing to lose, I mean hell, if you get caught you know you're done for the rest of your life so 'just go for it.' There are very few second chances, and almost no third chances. So in my opinions, prisons haven't become a place to punish criminals, they've become a place to get rid of them forever.
Keep in mind, the prisons I'm talking about are the majority of minimum or medium security facilities managed by counties. I'm not talking about the super-max industrial complexes. That's a whole different ball-o-wax, yet it does seem that they are growing while the others are shrinking due to the reasons cited above.
2.5 cents. Caveat emptor.