The thing with streamers playing slots is that basically they are getting paid to do so.
They basically are creating ads for the casinos by playing those games in the streams, and they get money from that.
These days ads can appear in many shapes or forms, even as content itself.
Besides the fact that they are paid, for many players it also becomes obvious how it works. This happens not only with slots, there are also bettors who are paid to make predictions and make and show how they bet on their predictions. On the one hand, this can be perceived as entertainment content, because they make a lot of predictions, all of them superficial without much analysis and I even admit that the casino either gives them some kind of budget for this, or even gives them access to a demo account on which they do all this.