Has anyone studied why homeless people refuse help? It's usually because the "help" isn't help. E.g. "you can sleep here but only if you haven't used drugs in the last week, so we'll test your blood before we let you in"
I understand that you cannot reason too well with an addict, so it might be surprising to some that somebody would refuse shelter if it meant being clean.
Still, what should be the approach then? Unconditional help?
I think it's a tough problem to solve: how far should we help drug addict in their addiction? Is the goal to help them survive, help them stop using drugs, help them find a job?
Depending on the metrics you will find that unconditional housing is more effective (ex: https://www.utoronto.ca/news/housing-first-more-effective-tr...) or offering incentives to stop is more effective (ex: https://www.chcs.org/resource/contingency-management-for-adu...)