Because it's much easier to squeeze in-person employees harder.

I'm being facetious, but I don't think it's entirely a bad thing. I'm not sure if you've even worked in a fast-paced environment where everyone is absolutely buzzing, but it's quite exciting and I'm not convinced there's a remote equivalent.

Alternatively, WFH employees have way fewer benefits (no in-office coffee or food, potentially no internet or equipment support beyond a laptop, no electricity, HVAC, refrigerators, badges, security, commuter benefits, etc) and don't waste 1-3 hours per day commuting to and from the office + parking costs + 1 hour just to get too and from crappy unhealthy lunch spots.

Their hours are much more flexible -- if the desk is right in your house, it's not crazy to hop on the computer quick before bed to finish up a report or send an email or review a PR. So when "crunch time" actually happens, WFH employees can spend more time working than in-office employees, and work less afterward to avoid burnout.

The flexibility has additional benefits for coordination across time zones: I work from home, and I can get up at 6 AM to meet with folks in Australia from my home office. Or I can take off early and come back at 8PM to meet with folks in India. Not an option for in-office work. If you try, you'll be taking the meeting from your couch or some other suboptimal spot, not a home office.

If your company is upwards of 5,000 employees, you probably have multiple offices. This means most of your meetings are in conference rooms with a video call anyway. Effectively no different from WFH meetings, except for crappier volume control, microphone gain, and visibility.

Seems like for giant companies, WFH is a no-brainer for coordination purposes across multiple time zones and physical locations. And for small companies, WFH is a no-brainer because there's a ton of static-cost overhead that comes with physical offices.

See, the problem is you used logic here, unlike senior management.