what if the money or account they are using is not their money or account? Is it an account from the gambling platform that they let the streamers use in order to promote the platform? I can't ignore the fact that a theory might be possible. Anyway, what do you think? or can you say about this streamer transitioning to streamers whose content is gambling? Feel free to share your insights.
So you're basically asking about two different things here? One of them is the probability that the streamer is practically tricking their viewers into promoting the service, while the other is the risk of underage viewers who might gamble because of him.
I don't think this is exclusive to gambling marketing activity. I remember reading a claim saying a streamer is using a demo account of some sort when they advertise an exchange. Even you can find the same thing with gacha game (you might argue they are also gambling activity, but that's a different discussion). I think there is no solution to stop this unless you want to bring legal issues and so on. As a viewer it will be better to assume they don't spend any money when they gamble, so just look at the features they're showing you. It is a bit naive to decide which platform you will use based on whether a streamer is making money from it or not. CMIIW.