Personally I used to use Pidgin, but since I moved my XMPP to Gajim because of OMEMO I have no need to stay tied to it necessarily. So I'm looking to expand my horizons, and I figured here's as good a place as any to start a discussion about Linux IRC clients.
I'm guessing it's because IRC is proven, robust, simple, and has established communities. It's also extensible and can be run on anonymous networks like i2p