I think it’s because it’s great for group messages too. SMS/MMS is kinda shit, especially when somebody has an iPhone and their iMessage interferes (seriously, enough of the ‘loved an image’ spam). IRC gets blocked on a lot of public networks because of its association with piracy, so that makes it less than reliable.
Discord is pretty full featured too, like IRC doesn’t do group calls, and getting a group phone call going is a pain. Being able to have different channels is also super nice, because you can have a channel for, idk, birthday party planning to keep it from vanishing in the general daily chitchat. I’ve used it with roommates to get everybody on board with a grocery list before, because we all had Discord accounts anyways.
It’s just useful enough as a community tool.
Not the person you’re asking, but I mostly watch craft stuff, particularly 1:12 scale dollhouse miniatures and sewing. The most recent video I could find that was even remotely relevant is several months old and about a different kind of miniature.