That assumes everyone lives in American suburbia with one extra room for your home-office. Guess what, most of the knowledge workers live in dense cities with tiny apartments. Average flat sizes for various cities (sqft): Bangalore (1260), Singapore (667), Tokyo (710), Paris (520) etc. See this image for more details: https://files.buildworld.co.uk/average-home-size/03_Average-...
To make it permanent remote would involve a huge restructuring of those societies and that cost is much greater than maintaining office towers.