They are in the other cities, but it's a network effect. The most interesting jobs are in SF, so they move to SF, so when people make new interesting jobs they do it in SF because all the people are in SF.
As I said, I hope this trend reverses as more people accept remote work as a good way to do business. But until then, it is what it is.
I suppose that all depends on what kinds of jobs you consider to be interesting.
At the very least, those who believe the most interesting jobs are in SF congregate there. And people who create jobs matching that belief do it there.
As I said, I hope this trend reverses as more people accept remote work as a good way to do business. But until then, it is what it is.