A comment I've seen a few times is that remote work highlights the minimal value that middle-managers provide to companies.
If you're employees work from home with little interaction with their managers and they do it well/better, then why have those managers? Like you said, companies want to be cost effective. So the push back to the office could be coming from managers who don't want a light shined on their lack of value.
What a world it would be if everyone had minimum 50mbps internet. "Good" rural internet is 1mbps for a lot of peeps, and a whole lot more people have a whole lot lower speeds.