I don’t think any government is giving homeless addicts cash to pay their rent, that would be insane.

What happens is that the addicts can get the money either from some other government program, or simply by begging, depositing cans, etc. The shelters don’t allow people to use drugs inside and they have a curfew. Otherwise, they would quickly become dilapidated drug dens.

Therefore, some addicts prefer to sleep on the street whenever they can afford heroin, and return to the shelter when they can’t.