Maybe there’s some advantage even because for the ones I’ve used a lot i know at a glance which part of steam they’re in, which wouldn’t be as easy if the only difference was the text. And each part of steam is usually internally consistent, at least mostly.
One of the major draws of discord is the fact that they host the servers for you, for free. Anyone can make an account, click a button, and have a discord server.
Afaik matrix does allow this (haven’t used it personally) but it’s something where I am a bit worried about hosting costs if it reaches a large scale. (Also unsure about how the matrix protocol works precisely, but if defederation is a thing which I feel like it has to be, I can see it leading to huge pains since discords use case is often about being part of a specific communitu, as opposed to twitter or reddit. Being unable to join a groip or see some messsges because of federation issues would be a major headache).