They are already tracking what the user owns, what the user has installed on the device, and needs to be updated on each device the user owns, hell if you have genius turned on they track how much you use each app, or listen to each song. But whoa buddy filtering a top ten list is way to hard?

to gain what To not annoy users and gain a little bit more of that perfection they are known for. Increase purchases by a few percent. Not striving hard when you are at the top is how you end up in MS, IBM, and every other fallen giant's shoes.