While the leases are fixed costs, it is not uncommon for a business to get tax breaks from the town/city/state based on the # of employees in the office. The logic is: more business in downtown (employees in the office) means more spending downtown (more businesses in downtown = more money for the local/city/state tax collection).
Employees in the office generate a lot of local-business money/taxes: lunch (food), coffee (life), parking fees, dry cleaning fees, childcare (somewhere), tolls to/from work, etc. A tax break is easy to justify if it means 300 people commuting to become customers every day.
However, the actual tax break dollars "saved" (not charged) is variable and depends on how many people are in the office (as opposed to the fixed-rate cost of leasing office space which stays the same whether there are RTO employees or not). So, it costs WF more money to not have people in the office (because they end up paying more of their fair share of the taxes). To make matters worse, local/city/stare govts are increasing their tax rates to account for the low RTO/local business so WF is getting squeezed from a couple of directions.... all of which are "solved" if they can just point to the high # of RTO employees.