Since about the 1800's Anglo-American jurisprudence has included a strong tendency to view the underpinnings of incarceration theory as a treatment model. Back then, our system was coming out of a particularly harsh period of punishment when a large number of felonies carried only one punishment: death. Reformation of that system came at least partially as an attempt to save the souls of convicts. After all a "cell" is the living quarters of a monk and the thought behind locking a criminal in a cell (with a Bible) was that he would examine himself, read the Good Book, and come out a new and better man.
Of course, like all nice, well reasoned, and well meaning theories, once you examine it closely enough to view reality it gets messy and the theory gets off the rails - usually fairly badly. How many criminals went to prison, were furnished with a Bible, and came out better men? I don't know and you don't either. However, I'm willing to bet that a lot of people who read that question smirked in disbelief that many did. I'd also bet that a lot of prisoners learned to say the right words and phrases to play into the system and sound like they were repentant souls when they went back in front of the courts of their day. On the other hand, some percentage of them were surely helped and we will never know how many. This is problematic.
The difficulty with "treatment" instead of punishment is that it almost never yields concrete, easily understood, irrefutably good results. If the current level of inundation with social media had existed when the system was reformed so that felons were imprisoned over a long periods instead of hung or decapitated, I'm sure we would have plenty of examples of tweets, blogs, and videos with people railing against the "wussification" of the system and complaining that there was no proof that the newer, more expensive model provided better results. And they'd probably have been right because people who are still alive will re-offend while dead people won't. Without a doubt, the recidivism rate experienced a rather large increase.
All the above is in the way of saying that penological behavior isn't entirely linked to practical reality, but it's strongly influenced by the philosophy that people bring to it. If society is in a more "realist" zone it locks people up to remove them from society and provide an example of what will happen if others engage in the same behavior. If it's in a more "fix'em" mode it engages in whatever the well meaning of that time think will make the criminal "better." In the past this meant trying to save their eternal souls and getting them to act correctly as a moral matter; in modern times it means mental fixes meant to get people to behave better as more of a self help idea. If a society is in more of an "equipoise" mode it will try to punish at a level which balances out the crime. Of course, the reality is that while the societal treatment of offenders varies as different beliefs come to the fore none of these has ever entirely excluded the others.
Lately, the trend is to roll back the reform of imprisonment. Somehow, I doubt those wanting to roll back imprisonment are advocating that rabbit poaching and pick-pocketing should result in the imposition of the death penalty. I could be wrong. Maybe the deep, long term goal of the head prosecutors getting elected in the big cities on promises not to incarcerate is to bring back the olden ways. Who knows? I can't read their minds any more than y'all can and it's a little cynical to believe they are just doing it because that's the political promise that will get them elected.
Lately, the trend is to roll back the reform of imprisonment. Somehow, I doubt those wanting to roll back imprisonment are advocating that rabbit poaching and pick-pocketing should result in the imposition of the death penalty. I could be wrong. Maybe the deep, long term goal of the head prosecutors getting elected in the big cities on promises not to incarcerate is to bring back the olden ways. Who knows? I can't read their minds any more than y'all can and it's a little cynical to believe they are just doing it because that's the political promise that will get them elected.