It certainly has its issues, but there are much worse market distorting policies that I would like to see be fixed before rent control gets put on the chopping block.
It is absolutely not in owner interests. But cities by and large have been built in accordance with owner interests.
Rent control prevents rents from aggressively dropping because landlords know the rents can’t be increased later. This is during a time when rents really need to go down.
" In determining the lowest gross rental amount pursuant to this section, any rent discounts, incentives, concessions, or credits offered by the owner of such unit of residential real property and accepted by the tenant shall be excluded. "
Civil code section 1947.12.
"Affordable housing" is a completely separate issue.
In a city like SF, vacancies is not a thing. Actually for that matter, in any market the market price is some equilibrium price that gives a certain vacancy rate.
Here is one of many papers: http://www.socsci.uci.edu/~jkbrueck/course%20readings/gyourk...
As you mention, a significant percentage of tenants with rent control would be regarded as "high income" households.
Hell, I know a guy who has a rent control units for a couple decades. He can pay his monthly rent with one day's take-home pay.
It sounds outrageous, but I know someone like that too. Got a rent controlled box in Berkeley as a student, never left. Rent is only about $700 a month now. If you make $180,000 a year, that's a single day's pay.
Not to mention the homeless.
Don't get me started on the housing "market" and rent control impact on supply/demand. Housing is largely an adversarial game, not a win-win game.