Tax reassessments during the boom of 2001 to 2007 were on track to price a lot of people out of their houses based on their current economic status. Proposition 13 and other bills passed across the country allowed individuals to avoid being "taxed out" of their house.
If you have a job that pays $100,000 and the taxes on your $250,000 house is $7,500 (3% property tax) and the tax quadruples to $30,000 in five years; why would you want the market fluctuations to be able to force an individual to leave their house?
The main item with this problem, as is with all affordability issues is that supply is not meeting demand. Look in Detroit and Flint where there is not enough demand and the supply is worth next to nothing.
Author's points of increased units would lead to a drop in prices until it becomes affordable to all. San Francisco will never allow it because the people who live there want to keep it San Francisco and NIMBY rules.