The usually-cited reason they should is this, from a letter to the Daily Telegraph:
For the employee, interpersonal contact in the office promotes problem-solving, communication and the generation of ideas. It reduces isolation.To which I say: BS. Or rather: that may be true in some places, but I haven't worked in any of them for the last twenty years.
Isolation is what you feel:
when you cannot talk, write, or even use a facial expression, without first estimating its reception by the audience
when you are surrounded by people who feel they can police what you say and how you say it
when there are corporate policies encouraging certain styles of communication, and penalties for failing to go along
when the decisions affecting you and your work are made by people you never meet for reasons that have nothing to do with any of your concerns
when you are in the middle of an over-crowded open-plan office, and for days on end, everyone you need to talk to is on a conference call, in a meeting, or just doesn't have any time to help you problem-solve and generate ideas
when the people you need help and replies from, can reject your request because they "don't have the resources"
when you cannot get a budget for the things you need to do your job
when you cannot get the support for the things you need to do your job
when you are the only person in your team using the skills you use and have the knowledge you have
This was the daily life of most of those Civil Servants and other Big Office workers in 2019
Why? How?
A lot of employers spent much of the years between 2000-2019 making their offices less and less pleasant places by spending less and less on the buildings.
Where once there was a seat for everyone, now there is a seat for just over half of them.
Where once everyone had their own place, now nobody does.
Where once Directors and other Big Beasts had their own offices, safely away from us Little People, now they are scattered around the floor and we Little People can't relax, communicate and be creative, in case we're doing it in the wrong way.
Where once you sat with your team, now total strangers can perch amongst you for a day. They never introduce themselves and avoid eye contact, so nobody talks all day because it might be someone from HR, Audit, or some other internal policing group.
The quality of HVAC (heating, ventilation and air conditioning) got worse and worse, because the requirements are based on building size, not occupancy.
The offices smelled of food from 11:30 to 14:30 every day.
Don't even ask about the toilets.
This too was the daily life of those Civil Servants and other Big Office workers in 2019.
The horrible quality of office life in 2019 was the main reason people packed up their laptops and went home so willingly in March 2020.
Nobody is talking about this.
If "working in offices" was so beneficial, nobody would need to make people do it. But they do, so it isn't.