Because, at least from my software dev perspective, if upper management realizes how easy it would be to make someone on the team a "team lead" pay them a smidge more and then use metric tools to make sure stuff got done there would be no need for middle managers.

I work for a fortune 500, tons of beauracracy, and the people always moaning about people being in the office are most often the least useful people in the building. Lording over people's cubes "keeping tabs" is seen as a way to tell their bosses they are valuable.

Ive said it so many times to my boss who is on my side and has fought for me to WFH: "If I stop working you will know it instantly, things won't work and besides theres an entire dashboard I have to self report my progress to which again I can lie on for a bit, but will be obvious if I do so longer than a week".

There's also another factor of the sunk cost fallacy, many corps own buildings or are on long leases, leaving them empty looks like a massive waste of money even though tbh leaving them empty by my assessment would actually save them money.