Keeping things just good enough that search users return is not the same set of incentives as delivering search that meets the comprehensive set of user wants.

Your instinctual reaction to frame this in the context of a market is faulty. ALL of the major search players operate under the conceptual mode of users as product, advertisers as customers. The same is true with other media companies (TV, newspaper, etc). That seems to be the only model the market will currently bear, as the existence of media giants is predicated on their ability to accelerate consumption