The reason it's analogous to water-cooler talk for each person to have their own channel is because when you go to get some water, and see other coworkers milling about, you're going to know which coworker you're interested in talking to, who often has interesting insights, who might have something interesting going on in their personal life that you'd like to hear more about. So, in the absence of a common meeting space, you can go check out the channels of people you're interested in, and scroll through to see if they've got anything interesting going on in their life.