Well, I'll provide some explanations
1) Self-Employed and subject to fickle income at times due to audience tastes: This is probably one of the biggest things - Outside the big streamers who can become part of an agency that will get them benefits (like disability, medical, etc), you're essentially on your own. Get sick? Get tired? Tough luck. If you take a break, then you can experience a significant erosion of viewers and thus income. This is part of the reason you see lots of streamers chase "metas", like reaction content or specific games. They want to stay relevant and try to cater to ever changing audience tastes. This is especially true if viewers aren't there for the streamer in general, as in they like the streamer and find them interesting no matter what they are doing. However, even that has limits. You see plenty of streamers who would rather play specific games on stream, but because they aren't very popular, they can't because it hurts their income
2) Parasocial/fandom: Streamers aren't unique in this regard - pretty much any public figure with a fandom is going to have this. But there is an added level of stress where you have to pretend to essentially be the audience's friend/interested in their likes, while at the same time trying to guard against overzealous fans knowing too much about you. Especially many female streamers, where you get the psychotic stalkers (males can get them too, but you definitely see more with female streamers). You can tell which streamers have learned hard lessons about this. Ones that has been in this for over 10 years will not show any windows or outdoor shots, refuse to give any specifics or house tours, because they know there are some hyper fixated people that will spend 100+ hours on Google Maps trying to look for a house that has 2 shrubs next to a white lamp pole or whatever it may be.
3) They hate their job: This combines #1 and #2, but at some point you just hate the job because it is no longer fun. You're a slave to a game or meta. Ninja was absolutely sick of Fortnite, but he was forced to keep playing it because it was what brought him views. At some point, you're basically in a job that sucks any enthusiasm you may have about the job.