I missed your response, my bad, but I think others have touched on the major point with some pretty good analogies, but I will give you a full response since is a valid question. DISCLAIMER: I am a Software Engineer, not a real estate expert, although I was raised by a real estate expert.

Imagine you are Apple and own "Apple Park" in Cupertino, California.

Apple does not own the property "out-right", they have a mortgage on the property and buildings similar to the average home mortgage, but much more expensive. When you "own" the mortgage, it is up to you who occupies the building, which often is done by contract. When you "own" a building for the purpose of giving your own employees a place to work, you often enter in a contract with "yourself", but most often as a "subsidiary" signing a contract with a "parent company".

Let's say that a subsidiary is "renting" the entire building, but also, 90% employees work remotely. Although you, as the subsidiary, are still "paying rent to" the parent company, you as a subsidiary are losing money by paying for an office space that is mainly unused. So sure, it could be said that the parent company "isn't losing money", however, the subsidiary is since the office is unused and still being paid for. The subsidiary can't just stop renting the office, since they are in a legal agreement with the parent company. This pushes parent companies to enact "return to office policies" so that subsidiaries are paying rent on "required office space". Having "butt's in seats" also helps with maintaining building value as one can prove "hey look, my office building is in demand", even if simply artificial demand through subsidiaries.

Most office buildings, especially if for tech, cost in the hundreds of millions depending on location. If you think tech companies buy them outright rather than mortgage them with the company and assets as collateral, that is incorrect.

In other words... If you have a mortgage on an office building with no one in it, the "market" looks negatively upon that, which brings the building's value down, but not your mortgage payment and interest. Therefore, you are paying more on your mortgage than the value of the building. Similar to buying a car with a car loan, using the crap out of it, and then not touching it for 5 years and expecting it to increase in value. (Car is a bad comparison as 99% of them lose value the second they leave the lot, but is easiest to compare)