Each protocol serves a purpose - it's ORIGINAL purpose. To extend it like this means to degrade it's original usefulness, make it complicated to create new implementations and it won't even compete with a new protocol specifically designed for the new purpose. All this leads to "extinguish" phase.
IRC was implemented in probably hundreds of programs (many/most from scratch, not by importing the same library!). There's even an implementation for Arduino! It's a successful protocol as it is now. Could you run it on Arduino if it had WebRTC in it?
Probably not, but is it worth starting new projects with 16-bit MCUs in the year 2024? 32-bit MCUs are cheap and plentiful in offering.
I realize the IRC protocol is easy to implement (though the protocol itself has flaws that make it difficult e.g. to identify which message is a response to your query, IRC3 addresses this) and I too have done it in the past, but I see zero reasons to embrace it today.
IRC was implemented in probably hundreds of programs (many/most from scratch, not by importing the same library!). There's even an implementation for Arduino! It's a successful protocol as it is now. Could you run it on Arduino if it had WebRTC in it?