> If you allowed for zoning that would bring down the cost of rent, and therefore the cost of living, more people could get themselves off the street

Lowering the cost of living is probably a good idea, you're not wrong, but there are some people for whom it will never matter how much the rent is, because they're not with-it enough to organize themselves to be able to pay it or to be a reasonable tenant. Mental health programs are the only hope I have for dealing with that, but they're too underfunded and frankly too voluntary presently to make the real difference we seek.