@sporadica look up "Prevention Point Pittsburgh". Go to their website and see for yourself what our taxes are funding. I'm not even joking its one of the most disturbing things i've ever seen
Every major city (including Pittsburgh) does regularly cover up illegal graffiti. Pittsburgh also has a designated police graffiti squad.
Covering graffiti takes much more time, effort and money than the initial vandalism. Cities have to deal with budgetary constraints so the result is that it can take a while before any given piece of graffiti is covered. This doesn't mean they aren't doing it!