Really? I'm a dev (although not at Facebook) and I travel for work several times a year. Also, all of the remote employees I've worked with have traveled to the office occasionally.
dunno i’ve been fully remote for 6 years now. Many reasons people get together. Several times a year is my experience. Would be a tough pill to swallow to have to secretly travel to town, get a hotel, all on my own dime. What a huge stress & pain in the ass.
edit: In fact, “get the team together quarterly” is, last I heard, pretty standard guidance for distributed teams. I think it’s a fair assumption if you have little experience working remote. There’s more travel involved than you think though.