This is definitely a thing that happens. Some teams also do a lot of work in hallway conversations, and this sort of accidental interaction is critical. I witness this all the time.
I would much prefer that my company let me work remotely. The Bay Area is full, seriously, and I'd be happy to work from many other places.
But denying reality doesn't help.
I think there are potential technical solutions to this problem (VR office at home), but I suspect it'll take legislation (aimed at getting vehicles off the road) to make remote work a real thing that a lot of people do every day.
That kind of smalltalk definitely happens, but where it happens varies a lot. At some places probably 80% of the idle work-related chatter happens on the IRC/Slack, while at others it happens mostly in the coffee area or hallways. Seems to be a company-culture difference in large part. Both are ok for me, but the places that use IRC/Slack a lot are easier to be remote at (or even just on a trip) without being excluded from all the impromptu discussions.
It's actually not that noisy normally, just the clatter of keyboards.... until there are problems with something, then it can become pretty active. Most people stick with Hipchat or email for routine communications like getting stuck on debugging a piece of code or where to eat lunch -- unless they are talking in one of the break rooms, or they duck into one of the conference rooms. People tend to be pretty cognizant of the open office so if you hear people talking, it's generally something worth listening to.
I honestly do not believe for one second that this is a thing, or that it's a significant thing.