Definitely a good way to get your extra peanuts. I think that it takes so much more effort to get good leads so getting people to do the hard work for you via affiliate links is worth its weight in gold and I can see why companies love to do that. For every dollar you make they make 10 probably or something like that.
For influencers, this can bring in quite a good income, because they do not focus on just one direction, but I think this is more suitable for influencers with an audience that is focused on making some kind of profit, that is, a community with a financial subtext, and creating such for gambling is not easy, unless these are some channels with sports predictions, but in this case I agree with you that the audience will be limited and the income too.