Right, but the taxpayers in that city are worse off. That's why any solutions need to be driven at least at the county level and preferably at the state level. Leaving it to individual cities creates all sorts of perverse incentives. (SF is somewhat unique in that they are their own county so for that area specifically, shifting programs from the city to county level wouldn't change anything.)
Taxpayers are pretty much always going to be worse off helping the homeless. Only a small fraction of the chronically homeless will become tax positive citizens in their lifetime.
Either you start off with the first principle that it's OK for wealth-transfer schemes to make tax payers 'worse off' via compelled charity, or I don't think you can get to the point of supporting generalized homeless relief programs. Maybe programs targeted at short-duration stuff to get people into jobs that are capable of doing them and a housing contract might work, but it'd have to be extremely well thought out and wouldn't benefit most chronic homeless.
My point is that it's a lot easier to share the tax burden at the state level rather than in individual cities.