I know a lot of people on here feel like work from home is just as productive or even more so than working in the office, especially in the case of open office layouts, but it's just not universally true.
Some people are really good with responsibility, and some people really are not.
As an illustrative example, you might have 20% of workers working at 120% efficiency, 50% of workers working at 80% efficency, and 30% of workers working at 10% efficiency. This example comes out to about 67% productivity overall.
But you are still paying 100% of the salaries.
It would be nice if you could just tell the 30% who have terrible efficiency to come in while everyone else can work from home, but you can't. It immediately going to be seen as unfair. "Why does X get to work from home and I don't?!". Many people don't even have the self awareness to tell that they are terrible at working from home.
Another option would paying people for the amount of work they are actually delivering. Yeah, that isn't going to happen. I mean, for a start, it's hard to even quantify most of the time. A good manager knows who is delivering and who isn't, but you can't exactly point to number of bugs closed, or lines of code checked in to prove it.
And aside from anything else differing pay is a hard pill to swallow even without WFH involved. The guy earning 200k might be 4x as useful as the guy being paid 100k, or he may be no better or even worse!
My point is that there is no really satisfactory option here. I mean, you can make the argument "It's a pandemic, they should be happy to pay the same amount for 67% of the work" and sure, maybe that's just the way the cookie crumbles. I mean, lots of people are being totally forced out of business due to this pandemic so it's better situation than those guys I guess?
But you can at least understand that it's a sucky position to be in.