The worst thing about office friends is they immediatley cease to be friends when you are laid off or change jobs, only maybe 2% do I actually stay in contact with, and frankly that is just because of the nostalgia I have of working with them and the networking benefits. Work friends are not friends. People you meet near your home and at your book club are more likely to stick around through the thick and thin. That being said yes being in office can benefit some people's mental health
Genuine question: why do you expect them to stay your best friends forever? Is just seeing other humans not valuable enough? Your POV strikes me as very all-or-nothing.
You probably just never got to know them that well and did things outside of work with them. I've met people at the office and stayed in touch with them and hung out after they left or I left the company.
> Work friends are not friends.
This is reductive to the point of absurdity. Situational friends are still friends. How many of your elementary school friends are still your friends these days? High school? Summer camp? Heck college friends? Unless you're living in the same town with the same people, there's a good chance that most of them aren't anymore. Were these people also not your friends? When you leave that book club, when you stop showing up at the corner cafe, when you move out of the neighborhood, how many of those people will you still be spending time with 5 years later. For the ones that you aren't, were they also not really friends?
Friendship isn't a binary thing. Not every friend you make will help you bury a body, but not every friend or friendship needs to (or should) run that deep. And sure not everyone you're "friendly" with at work are friends, it's a spectrum. But situational friends are friends. People you bond with for a short while over a shared experience and then when life moves one or both of you on the friendship ends are still friends.