It's not NIMBY. The problem is between California law and San Francisco law renters have far too many rights. A person who knows how to play the game can stay in your rental for more than a year without paying rent. You shouldn't need to hire a lawyer everyone thinks is an asshole (think about that - someone who's an asshole even for a lawyer) to get rid of someone who isn't even paying rent.

Property owners sell off places they would otherwise have rented out or just leave them empty because it just isn't worth the risk. That is what constrains the supply. You'd be crazy to go into the rental business unless you had a lot of units to balance out the Inges of the world, particularly since once you finally evict someone like that you have to tear out the walls to get rid of the stench.