They think that by getting back to "building culture" they can pay people less. It's that simple.
I worked at a company for years that didn't work on a fun product, didn't use new tech, and didn't pay well compared to other tech companies. They were able to get away with it because of their "culture".
Now that that's gone since we've all gone remote, EVERYONE is leaving for higher salaries elsewhere and for more interesting work.
If they can get the "culture" back, they'll have less people leaving and won't have to offer raises to make people stay...