Anything that govt. funds quickly has an entire industry feeding on it and doing what they can to make it grow. Part of the problem that generates such a large prison population and that generates layers of additional laws and regulations each year is that the public demands it. Anything that goes wrong, any bad thing that happens, and there are cries for action to stop it from happening again, often from the industries that would benefit from increased regulation. As a society we often end up with solutions that are far bigger than the problem.
A different approach is needed. Just using drugs as an example being this is what is behind a huge portion of the prison “justice” system, if instead of putting people in jail for possession or use of drugs we instead held them accountable for the effects we’d probably have a lot of empty prisons. Note that even if drugs were completely legal I personally would not partake. I have no interest at all. By holding accountable I mean they go to jail if they fund their habit via robberies or such, or we deny them public housing and other entitlements if their drug use is a factor in their inability to support themselves, or they are caught driving under the influence, and so forth. Merely possessing or using would not send someone to jail as occurs now.
The same approach would make sense for gun crimes, another big industry. Merely possessing a gun should not send someone to jail as occurs in many jurisdictions now. Using the gun to commit a crime should.
It really is time for a re-thinking of why we have so many in prison.