I have no trouble making and sustaining friendships with or without an office, in fact only one of my (former) co-workers is an actual friend.

Regardless, something about the isolation of working from home for anything more than a day here or there is just too mentally harmful for me. A much lesser form of solitary confinement, I suppose. Even going out and doing things after work every single day is no cure. I've tried it on and off over the past decade, with and without a co-habitating girlfriend. With and without pets. I've tried working from coffee shops, working from parks, co-working spaces, etc.

For some it's not a matter of needing the office for friends, some people just need the office environment itself. Something about being there "in the shit" with your team, best I can tell, rings that mental bell.