Because they don't have to pay for those offices anymore. If the company is allowing for remote work, they can also downsize those offices (subject to lease conditions), saving piles of money. (Commerical space is expensive!) If some of those savings aren't passed onto their employees, those employees will choose to move to a different company that has a more general WFH allowance, probably get a raise in the process, and work with a company that's just generally less obtuse to work at/for.