I'd guess the important feature for Discord is it is easier for the administrators to get hosted and online, but "you could create a client with a better UI than discord" is a terrible line of argument. People could do lots of things in the OSS world and they don't. I can't recall any IRC client that I have found as easy to use as the Discord client except - ironically given the topic - ChatZilla which died off years ago because Mozilla decided that extensions were more of a 2000s technology than something they wanted to support.