San Francisco's zoning makes it illegal to build apartments in 73.5% of the city
I'm going to throw out an unpopular opinion.  I think it's great that 73.5% of the city is low rise.  26.5% of the city having apartments is already more than plenty.  100% apartments would destroy SF.  People fighting to get to live in SF because of its character.  Destroying that you won't have San Francisco.