cos irc just works. It worked just fine 20 years ago. It worked 20 ish years before that. In 20 more years it'll still work.

Any idiot with some time and a computer can throw up an ircd and host a server for people to chat on. Every other chat program either requires some random company to host it, or a much deeper knowledge of computers and software.

The clients are available for every system around. From tiny little simple single connection clients, to massive complex graphical systems. You want to chat on plan9? There's a client. An ancient amstrad cpc? There's a client. (That one might be a bit more challenging) Android, Linux, Windows, Mac? All of them have clients, most of them multiple.

I will say, I like Matrix, I like XMPP, I am not a huge fan of any of the chat clients with a single point of failure like discord or teams or whatever. But IRC is still my favorite, and probably will be forever.

I just have it setup the way I want.