It's about expanding the audience. A lot of the people going to twitch are there for the normal game streaming, they don't go to the internet specifically looking for thots. But when they see it, some of them get pulled in, and the simp audience gets expanded. They're mostly men (or boys, in this case, which makes the whole thing significantly more unpleasant) and they already obviously have a desire for the streaming "relationship", so they're a rich source of future thot onlyfans audience.

Getting a new audience is often easier than getting someone to change their preferred brand.