I don't entirely follow, though; the idea is that you want the people who pay you to be satisfied with what they're paying for so that they continue to do so, convince others to do so, and are willing to increase their spending. If that wasn't the case, there wouldn't be a conflict of interest for advertisers in the first place.

There's reasons that the incentive to keep the users satisfied may not be followed, but it's mostly tangential, and relates more to other forces than it does where the money comes from.