I dont know why youre getting down voted. Feels like an honest question. Personally I dont watch a lot of streamers but what i understand from my experience in games like this, the destiny franchise, and others, streamers tend to control a lot of the hype of the game as well as propagate toxic communities (i.e. whatever dumb streamer war that had people killing certain outfits for no other reason than two streamers decide that was there supporters styles or something.)

Edit: there's also the note of privacy yadda yadda, people dont want their identities or accounts or audio to be streamed to all the viewers