I'm not sure if approving a bad app hurts Apple. If the app is truly awful customers can get a refund. Also the app store has some sort of collaborative filtering in place. Namely apps that are highly rated and/or downloaded a lot and/or some other reasons bubble up to the top. So apps that stink will just float to the bottom.

Is Google hurt when a bad webpage makes it into the search index? Not really. In general it just floats to the bottom.