How different is that from at-will employment though? You can be fired at any time and for more or less any non-federally-protected reason (and can quit any time too). That seems pretty uncontroversial in the US at least.
The parallel doesn't really exist for Twitch. Other than perhaps YouTube, are there any platforms that would get you anywhere close to the pool of potential users on Twitch?
It has a little something for everyone.
But let’s take a step back here - no one is entitled to be a Full time professional streamer. Say you do something egregious (or not) and get banned from all streaming sites - just go get another job? Twitch doesn’t have a monopoly on employment.
But in the Twitch, YouTube, Amazon, etc. cases there is no other platform that pays the same.
Did you not just enumerate 3 different organizations in your comment?
Do "Twitch Streamer" and "YouTube Streamer" really constitute different "jobs"?
(I mean, to the extent that they are "jobs" at all, I consider them the same "job".)
YouTube: Youtuber
Twitch (as discussed elsewhere in the thread): eSports tournament competitors