Scarcity results in rising prices. In general wealth creation comes from productivity. There are many in society including special interests that are not interested in creating wealth but taking it for themselves while harming society as a whole. That includes not only wealthy landlords but many other groups of people don't want competition.

Another example is limits on taxicab medallions (which we have in NYC) so that medallions in NYC were valued at $1.2 million each and higher fares for passengers but that scarcity was fixed by competition from Uber/Lyft so that now medallions are only worth $700,000 or less and fares are less expensive than they were.

Another example is labor unions. Various forms of tariffs also create scarcity benefiting the special interests over the needs of the general population. Many jobs have extraordinary educational or licensing requirements to create scarcity and limit competition.

When it comes to housing wealthy landlords want their land to appreciate so they lobby politicians to pass these regressive laws. Without spending a cent, simply reversing the artificial scarcity in housing means that renters pay less for rent and more for goods and services, the construction trades have jobs, etc.

Here's a bunch of my YIMBY readings:

https://bendyimby.com/2017/06/12/yimby-reading/

It's a simple math of demand and supply. Density restrictions keep supply in check it keeps it constant, but demand grows exponentially over time, due to immigration and population growth. Thus price grows astronomically high. If you remove restrictions and with the right technology you could create housing that keeps up with the demand growth. SF homelessness is really about incompetence of city politicians, bureaucracy, and the lack of good talent in public service. Why would I want to work for the city to make it a better place when companies inside my city or just further down to the south pays me 3x or 4x what they're offering.