They do this because they're not traders but influencers, they only claim to be traders to connect with their audience as that's the perfect way they can use to influence them.
The fact is that some traders do live trading, if their portfolio is good and can be confirmed, then more and more people come to subscribe which makes them truly influencers by their profession. Affiliate programs are one form of passive income that can't be ignored when it comes from large companies.
as long as the influencer is truly an experienced trader and shares their trading activities well. in the sense that there are also platforms that collaborate with influencers to promote their platforms. so maybe what the influencer is sharing is not the real experience. I see this quite a lot on gambling platforms, but it doesn't rule out the possibility that it is also done by exchange platforms.
Regarding Affiliates, everyone can do it. and that will be passive income that can be obtained apart from trading or streaming activities. there's nothing wrong with that. everyone deserves to grow their income. the most important thing is that they do it well and don't aim to create a pump and dump scheme with the streaming videos they make.