Just speaking for myself here (maybe I'm a sociopath); I would be "friends" with my coworkers because it was the expected decorum. In-office I don't
want to be anyone's friend; I want to get stuff done. I appear friendly in the office because it is the expectation and much easier than trying to isolate myself. Remotely, the tables are turned; it's trivial to isolate myself, and I have no expectations of fraternizing with my coworkers.
If you are so lonely that your coworkers are your only meaningful support network, that's a sign you need more friends.