They get huge tax breaks for the bodies those buildings were supposed to bring to their cities. Now that nobody’s in them, those cities aren’t getting the extra tax money from the office workers anymore, so they’re pressuring companies to bring workers back to the office. No giant, money-thirsty corporation wants to maintain a huge, expensive office building, but they’re stuck doing so unless they want to sell it at a loss and risk pissing off the owners of whatever palms they had to grease to get the deal in the first place.