I think that's because not many people use their discovery. They usually end up from somewhere else. So they don't have that part to play with (eg charging money or using algorithms to recommend content that's profitable for them).
Also, their monetisation is pretty seamless because you come there with the intent to pay. So requests for payment don't feel out of place.
I guess for the people you patron it's less great now because I see many people moving to ko-fi.
