I had been working remotely 2 days per week (Mon and Fri) before COVID and there are both pros and cons.
Commute. You definitely save money on that, but time? I'm not so sure. 40 minutes of train either direction is over an hour of reading books. I sure as hell do not read for an hour per day when working from home.
Food. At the office I have choice to bring my cheap and healthy meals from home or eat something greasy and indulgent from a local restaurant. And nobody is counting how many cups of coffee I have per day. Only crappy suburban delivery at home, and healthy stuff gets so boring if you eat it every day for months. I spend a lot on hot sauces now. And also I gained some weight despite running 100-110 mpw and eating that healthy crap.
Equipment. I love working on my Mac but I fear the day when I have to buy a new one, it's so expensive. And my current one is 5 years old. My workplace at the office has two huge screens and a super comfy chair that's about as expensive as my laptop at home and I don't have to pay for that. Also phone, printing, supplies.
Training. Doing doubles is harder when you're at the office, but I somehow got into the rhythm. Worst thing that happens you're sweating at a meeting. You also don't do am long runs on an office day. When WFH, you sometimes do that and you're done for the day, hard to accomplish anything else.
I've started working from office two days per week this month and I'm glad to be back. Not having an office to return when you need to isn't that great. Mixing and matching is the best. Companies could also save in this scenario by providing less workplaces and making them impersonal, knowing some percentage of workers would always be remote.