I think you'll find that many social channels are a well kept secret. No one wants to ruin a good thing by advertising it to the public. Use IRC for a while, explore the bigger channels, start channels for your friends, and eventually you'll find your way into other social channels.

There are plenty. Breakouts from them forming their own communities every few years. The base of our community has been around for at least a decade and the main channel is on its fourth iteration since I joined.

Telling exact channel names would out me pretty fast though I reckon.

Same in my 'social' bubble, started as a small gaming community that branched off a bigger one (you know, free forums, then a site, then self-hosted forums, IRC channel which later turned into a Skype group chat which nowadays is a Discord channel, etc). These things just form organically.