And if we did, what would be the difference? Sure, there would be no ads on the platform (plenty of sponsored content, though), but there would still be an algorithm. And it would be minimally different to the one that exists today. The current ad driven model doesn't allow paying advertisers to drive the algorithm. Rather it lets you drive the algorithm by your revealed preferences and then allows advertisers to target you based on those preferences and insert their ads in the result, which is much more effective. But if we didn't have the ads, the algorithm remains. The question "what does this user want to see?" is equally as relevant to a company that wants to convince a user to keep paying for their subscription as it is to a company that uses it as an advertising vector.