Let's not generalize but somehow there are people who's earning a living in gambling, Don't forget we have have pro poker players who earning a fortune by playing, read the article here
https://upswingpoker.com/top-ten-best-poker-players-history/ but this is a skill based game though. But if we talk about luck based game then I will agree with you and even popular streamers cannot get a continuous revenue by just solely playing.
Yeah I think a lot of people are misled by the numbers. Yes, there are streamers earning hundreds of thousands, or even millions, but most of these are just sponsorships that won't last forever. And trust me, in general, they put a lot of it back into their gaming. It's not going to be sustainable for a lot of people. Can't ever generalize anything, and very few people realize that only skill gets you a job in the end.