You'll cross-pollinate across functions. Or at least increase the chances of that happening. Not saying that's worth the tradeoff. But my time in the office often finds serendipitious value in random off-team conversations, not scheduled time.
There are, however, a few times when getting together and discussing something in person is valuable, but this is no more than maybe a couple times a month. I can definitely see this being different for other roles.
Obviously varies by culture. And while I've never worked for Meta, I've been at your Mountain View and New York campuses more times than I care to have been. Everything–including communal spaces–seems laid out for individual work. (This was true before the metamates nonsense, though that obviously accelerated it.)
I worked at Meta nee Facebook from 2013-18, and back then there were no documents, and the only way to figure stuff out was either spelunk through the source code, or talk to people in person. So I was very surprised that they ever said they'd be doing remote, and entirely unsurprised that they are moving back towards the office.
That being said, there was no tracking of in office/remote days, it was just expected that you'd work from wherever worked best for you but (almost) everyone was based out of an office.
Frankly, the ones that tend to play, goof off and shoot shit together. And it’s not necessarily companywide nor evenly distributed. But it’s something I value tremendously in work cultures, both because it’s productive and fun.
I mean, I've heard good ideas being discussed, but at the end of the day we all have our in-progress projects and tickets, and future projects already planned out, so those good ideas never make it to fruition because everyone is busy anyways and doesn't have the time or resources to do anything about it. So in reality, those "cross-pollination" talks become nothing more but socialization moments, which is fine, but to force everyone into a miserable commute just to achieve a bit of socializing is insanity to me.