From an architect:

• Land surveys: SF is very hilly which makes building hard
• If you want to demolish an existing building:
  • there might be a lot of things that are not up to code that you will now be responsible for like redoing foundation, sidewalks, etc
  • might be historical zones where you have to adhere to certain aesthetics and keep the facade of a building up, and then rebuild around/behind it
• If you want to build in a dense populated area:
  • shut down roads and hire extra people to direct traffic to bring concrete, etc to work site

From an economist:

• any supervisor can veto
• there’s less incentive to build housing as opposed to commercial buildings, which you can charge more property tax for
• usually there is an affordable housing clause to every new construction

From a local politician:

• SF has a lot of small zones with different requirements
• corruption in government