There is a pretty big door opened for Amazon on the iOS platform. For whatever reason Jobs did not push an Apple bookstore like he could have and although iBooks is a decent (not stellar by any means) reading app, the iBook store is rather limited. Amazon excels in digital books, so through that open door to iOS Amazon can generate a huge amount of sales. So I guess from a business sense it make perfect sense to put a lot of effort into the Kindle for iOS app because of the huge numbers of iPhones, iPads, and iPod touches. I doubt we would ever see any genuine sales figures, but I venture to guess that a significant percentage of Amazon's digital books sales are directly related to people buying them to read on an iOS device. I would also venture to guess that a significantly lesser percentage of Amazon's digital books sales are directly related to people buying them to read on an Android device other than the Fires which have their own Fire app. It just makes sense to put the most effort where the most profit is, and it ain't with non-Fire Android devices!