A coworker ragequit the common channel after people said "hello" in there, literally. (He couldn't figure out how to disable notifications, apparently.) Now the only traffic in there is when somebody accidentally clicks the wrong channel.
Channels exist, direct chat exists, but it doesn't work unless people are super super meticulous with setting their status, and even then "hey" is more intrusive than sticking your head in somebody's open office door and seeing if they're busy.
I think we had an all-hands meeting at some point around Easter, those used to be weekly. Please don't ask me what anybody in this department is doing, my line manager is a fool and without tapping a diagonal manager for information three days a week over morning coffee, for all I know we could be a Win-only shop by now, nobody would've told us.
Yes, I'm just venting.