Many are mentally ill, not sure who would hire them, easy to say "get a job" but they're literally crazy. And if they're not crazy, but heroin and meth addicts, then adios to your tools and equipment when they're chasing a high and out of money after the first payday.
Part of it is from defunding mental institutions.....oregon and wa both gutted theirs. Asylums got a bad rap from human experimentation and twisted things done in the 1950s, 60s, 70s, but we need them...and could just not do that bad stuff to people. Its also near impossible to commit someone involuntarily anymore, whether from court rulings on freedom or whatever else, something changed from 40 years ago, so if they say "I don't want to go", nobody can make them, and they're on the street.
The other half with addicts: need to enforce laws against crimes fueled by addiction and force detox. Right now they get a free pass, and because they know there's no downside to stealing, because they have 0 chance of getting penalized, they do it more... But if they started getting sent to jail and forced detox when getting caught stealing/crimes related to drug addiction, it acts as a deterrent the next time they're considering breaking a window/stealing stuff, there's negative feedback to that action embedded in their brain, there currently isn't any deterrent. Also, forcing them into detox gives them their life back even for a moment, if they want to go back to using drugs its a choice, and when they're committing crimes to do drugs again, they get detoxed again. Its not pleasant to detox, it may even be enough for some people to avoid meth/heroin once their clean, but if not, maybe the 3rd or 5th time being forced to quit will sink it in for them.