So people can post drawings of their own Minecraft sonas but not other people's sonas? That just doesn't make any sense. Sounds like you're a hateful person tbh :(
I have no intentions of being hateful. I'm not running this blog out of a desire to shut down all mcyt fan expression— I'm an mcyt fan myself!
The logic I'm working with is that posting about your own or a friend's experiences with the game (builds, skins, OCs, minesonas etc) is the intended use of the minecraft tag.
The issue with applying the same logic to youtubers* is that the audience for MCYTs is massive. So instead of a handful of people showing how they imagine themself in-game, it becomes hundreds of mcyt fans talking about their guy's latest upload. A guy that the average Minecraft player might have never heard of, and has no interest in seeing in the tags of a game they like.
And sometimes, said upload isn't even that focused on Minecraft as a game (in the case of more rp-heavy things like the Life Series, Vampires SMP etc). In those cases the fanworks etc tends to be centered mainly on character dynamics and the YTer's personal lore, i.e even less related to Minecraft.
*I think it's perfectly fine for aspiring and even established youtubers & streamers to self-promote using the #minecraft tag, since they are showcasing their own work. They just happen to have a larger follower base than the average Tumblr user.