Prior to the pandemic, whenever the discussion of being entirely remote had come up with my employer, the legal dept had stated repeatedly that they can't make WFH the official position, because OSHA requires that if a job is expected to be performed remotely, it is the employer's obligation to ensure that the remote work location meets the same ergonomics, lighting, fire safety, etc standards as the office workspace. And so we'd have to allow our employer into our homes to let them inspect smoke detectors, install new lighting, approve or disapprove our home desks and chairs and possible replace them.
Companies will still have to maintain office space, because actually making WFH an official thing is more hassle than it is worth.