Are you asking how common the free food/soda is, or the feeling of entitlement to it? The former exists where there's competition for employees. The latter is a pre-existing but latent condition that comes out in proportion to the presence of the former.
Personally, I've never forgotten that I'm lucky to have "extra" benefits, and I've never started believing I'm owed them.
I guess I haven't thought about competition for employees - I've only tended to think of the situation as employees competing for jobs. Does competition for employees only tend to happen in places like SF?
It's also this way in Cambridge, MA. And probably other places where there's more demand for highly-skilled developers than there are candidates. Maybe in smaller cities that are trying to bootstrap a startup scene.
Personally, I've never forgotten that I'm lucky to have "extra" benefits, and I've never started believing I'm owed them.