I agree with you but you shouldn't forget that most viewers of this kind of videos are very young and one part of them is not adult. Then there is a need to find a way to prevent them from being abused by those scammy/fake demos.
And this is the problem, if the audience of those kind of channels were people that knew that this kind of promotion is not real then there will not be such a huge issue, but many of those watching that type of advertising are people that do not have the experience necessary to know that what they are seeing is not real, and since they trust the streamer they try their luck in a casino due to that publicity thinking winning is as easy as what they saw in the video only to realize too late this is not the case.
Unfortunatelly there isn't a perfect solution for this issue. Scams/fake propagandas have always existed and people have been only able to avoid them through self awareness. Sometimes we have to fall for them to learn we shouldn't act the same way again in the future or in the best scenario we can learn with someone else's mistake. But inevitably there are always people falling for scams and at same time scams are always evolving and being adapted to the new technologies.
What we see on the internet now is just an evolution of the old streets' scams. There was the popular shell game usually promoted by an entertaining man on the streets, calling for the attention of the pedestrians around to give a try on his guessing game. But what wasn't told, was that there were 2 or 3 strawmen nearby, who would promptly accept the challenge, always winning the man easily.
So another pedestrians, watching that situation imagined they could win as well without any effort. However, once it was their turn the host mixed the shells much more faster, with superior agility skills than he did against his strawmen, in a way it was very hard to predict the correct shell, consequently leading the gambler to a loss.
I mean, the strategy of fake bets didn't start with Youtube or Twitch. It has been always around and just like streets' scams, people need to learn how to deal with them for their own good.