> I have a hard time wrapping my head around why companies are mandating 100% return to office.
Beliefs and dogma. Amazon's justification was "Amazon is an in-office culture." That ultimately boils down to circular reasoning; the key decision maker (whoever they are) has demonstrated an immense lack of critical reasoning. Continuing this practice is in the same realm as continuing other hostile workplace traditions, although it is one of the less serious ones.
In my opinion, it is wasting a lot of money in the form of productivity. Every employee who commutes to the office has an overwhelmingly high likelihood of having some of their mental resources drained. You're wasting a good hour or two of superior employee performance in the morning, and possibly some near the end of the day when employees start dreading the journey home.
> biggest factor is creating a culture of inclusion
This is a very important point. One of the major ongoing reasons that women are passed over for promotions is that they are the traditional/dogmatic caregivers. Home-first equalizes this, much like paternal leave does. If a home is unable to afford child-care, then men have just as much responsibility and distraction during work hours.
Some people may struggle to afford commute, for example, people escaping homelessness. Being able to work from home would reduce the burden on these people.
In addition, those who cannot causally/physically complete their job offsite (doctors, construction workers, tellers, baristas) won't have roads and public transport congested with people who have no business traveling to work.
> Dedicated offices were set up as "conference rooms"
We need conference rooms as an API. I should be able to add (and be billed for) a physical room to a meeting request as easily as adding a Zoom/GMeet - for when in-person collaboration is really needed. WeWork was in the ideal position to do this, it's a pity they doubled down on big corporate clients instead of "gig economy rooms."