>>49847593MMOs in general aren't good stream material for most cases. If you were like a top-tier PvP'er or raiding in a top guild maybe that's something but even then it's like, there isn't actually a lot of skill in MMO PvP and raiding is going to be generally quite boring clearing trash and watching the group bash its head against the wall wiping trying to make progress.
Not to mention with vtubers in specific, they are not streaming just to stream because might as well do it while they play as usual, they need to be interacting with the audience, or other vtuber friends/genmates etc as a default and that's just not going to be doable to really keep up doing for hours and hours every day. They're entertainers first players second in almost every case, and they can't really do both at the same time for MMOs. Or rather I bet you can smalltalk with your chat all day long while being a healbot or something but for actual boss fights and such, which could be literally hours worth of attempts for days and days, you're going to be a bad fucking member and wasted slot if you're too busy trying to entertain chat instead of doing your role.