The first company I worked for did everything on IRC. They were also by far the most successful company I've worked for. Coincidence?

Sure, and I still use IRC every day. But IRC+emacs is going to be a tiny fraction of the world, saying "this product is useless because there is an advanced alternative" is like saying "Oh, why would anyone ever want to fly commercial, it's so much easier and more fun to build and fly your own airplane".

emacs was just my example, but there are tens of IRC clients, from web clients to GUIs to android apps. Everyone can find a client they can easily used.