But why allow e.g. Chinese investors to buy property in SF if they aren't even going to live there?

1. It's only an investment because of limited supply.

2. Chinese investors buying up and not living there is effectively a myth. There just are aren't very many of them.

3. What's special about "Chinese"? If a rich NYC finance person buys a vacation home in SF is that ok? How about a Brit or German?

The supply may be limited because the people who own property want it to remain so.

Do they pay property taxes?

In California? With prop 13? Hardly.

We invented money as a way of distributing scares resources. When there is housing going empty while people live on the streets in tents with no running water, no electricity, no sewage, one has to realize that something's gone wrong.

I don’t think you understand how prop 13 works

The slow phase-out of prop 13 was voted in a couple years ago so it should become less relevant over time.

Maybe but that will certainly not bring down prices for the average US citizen looking for a home.

Why not?