Cultural inertia.

Wild but fun speculation: WFH decreases housing prices because people can disperse further. The higher the tenure & seniority within a company, the higher the likelihood of real estate ownership (both primary and rental properties). There is a conflict of interest in having more control on WFH policies and seeing your house not appreciating as much in value or not bringing as much rent. I wasn’t able to find data on this but it is hard to imagine any Bay Area exec not having real estate positions in the area.

More realistic reason: Middle management struggles with perceived lack of control and justifying their existence through wider WFH. Their business is their reports, and there is simply less control surface exposed through WFH to them. It is harder to carry out impression management from home. It is simply a higher friction, higher anxiety scenario. Ultimately they influence WFH adoption, whether at team-local levels or upward influence in company-wide decision making.

I can't speak for google but social herd psychology is a thing. And face to face communication is very effective for certain things. As an aside, every type of communication has it's uses. I think bosses in general feel much more in control when using face to face communication because it allows for fine levels of real time back and forth.