To be honest I never got that either, somebody scream for red or blue in front of a screen.
But at least for sports, you will see a level of play that is itself can be interesting because you can't just see it in day to day life.
Watching a video of a guy opening a kinder egg or playing badly at cod for the first time.
I get people watching streamers that are good at what they do. Rankers. Speed runners. Analysts. Jokers.
This is not what I'm talking about.