Because they aren't working for it tbh when they could.
They should be offered re-hab for free.
After re-hab they should then be housed in a publicly run business of sorts. given a job where their payment is a roof and three square meals. their work produces products which can then be sold to re-coup costs of re-hab and providing these meals and housing.
They are then free to stay there so long as they work and stick to the rules (no drugs, etc). The idea being that they use this experience to find a paying job and move out into the real world again.
Basically a full rehabilitation.
Work camps aren't "a full rehabilitation". It's been tried. It doesn't work. Well, it works in the sense of providing slave labour for unscrupulous businesses. But not in the sense of rehabilitation.