I'm curious what studies you have seen that jailing people helps them improve their life or stay off drugs. From what I can tell, that is not the case.

"The theory of deterrence would suggest, for instance, that states with higher rates of drug imprisonment would experience lower rates of drug use among their residents... higher rates of drug imprisonment did not translate into lower rates of drug use, arrests, or overdose deaths."

[0]https://www.pewtrusts.org/en/research-and-analysis/issue-bri...

Perhaps if prisoners actually received the drug treatment they needed. "To be effective for this population, treatment must begin in prison and be sustained after release through participation in community treatment programs. By engaging in a continuing therapeutic process, people can learn how to avoid relapse and withdraw from a life of crime. However, only a small percentage of those who need treatment while behind bars actually receive it, and often the treatment provided is inadequate."

[1]https://nida.nih.gov/publications/drugfacts/criminal-justice

But as things currently stand there appears to be "higher rates of substance use disorders in prisons and jails compared to the total population."

[2]https://www.prisonpolicy.org/blog/2024/01/30/punishing-drug-...

It improves everyone else's quality of life and it means they have the potential to access services. The individual homeless are certainly stakeholders but they are neither the only one nor the most important