I don't understand. I work remotely and regularly debug issues and brainstorm solutions with my teammates. Their physical proximity is not relevant. Clearly I am missing something.
You're missing that the point of being around people for some of us is to "interact" with them. I can easily interact with co-workers. I can not easily interact with strangers at a co-working space.
Also I work on console games. I can't hand the person on the chat the controller and say "how does this feel?"
It's nice to work on a problem with someone and then go to lunch and shoot the shit afterwards. Or just hanging out drinking some coffee. The key is you have to have some coworkers you like though, which I'll allow that not everybody has.
For me, I've worked in full remote and full in office jobs. I favor a mix personally. Maybe 2-3 days in office and the rest remote.