The same applies to the iOS App store though. After I owned Angry Birds, why on Earth did I have to look at it as #1 for years? Showing a top 10 with apps you already own filtered out is good for everyone. The top selling apps still show up for new users. After its purchased, it gives other apps a chance to percolate up, which means more sales for everyone, and more 30% cuts for Apple.
EDIT: I'd like to point out that the OP's reference to a purely "editorial" list has the exact same problem. I don't understand why the Apple ecosystem seems hell bent on refusing to take advantage of the digital age. Creating a one-size fits all top 10 list, or editorial list, is a fine strategy for a brick and mortar store where they have to show everyone the same thing at the front of their store. And mind you, this is the absolute easiest online market place feature you can possibly program: don't show me what I already own and thus am literally incapable of repurchasing.