why are companies trying so hard to have employees back in the office?

I have posted this on Reddit (askeconomics) a while back but got no good replies. Copying it here because I don't want to send traffic to Reddit.

What do you think?

I see a big push to take employees back to the office. I personally don't mind either working remote or in the office, but I think big companies tend to think rationally in terms of cost/benefit and I haven't seen a convincing explanation yet of why they are so keen to have everyone back.

If remote work was just as productive as in-person, a remote-only company could use it to be more efficient than their work-in-office competitors, so I assume there's no conclusive evidence that this is the case. But I haven't seen conclusive evidence of the contrary either, and I think employers would have good reason to trumpet any findings at least internally to their employees ("we've seen KPI so-and-so drop with everyone working from home" or "project X was severely delayed by lack of in-person coordination" wouldn't make everyone happy to return in presence, but at least it would make a good argument for a manager to explain to their team)

Instead, all I keep hearing is inspirational wish-wash like "we value the power of working together". Which is fine, but why are we valuing it more than the cost of office space?

On the side of employees, I often see arguments like "these companies made a big investment in offices and now they don't want to look stupid by leaving them empty". But all these large companies have spent billions to acquire smaller companies/products and dropped them without a second thought. I can't believe the same companies would now be so sentimentally attached to office buildings if it made any economic sense to close them.