Technically, they don't us it for their entire app market. They use it for the iOS app market when using desktop computers. On iOS devices, it is separate from

Technically, they don't us it for their entire app market. They use it for the iOS app market when using desktop computers. On iOS devices, it is separate from the iTunes app; on Macs, it is only in the Mac App Store app. Also, ebooks are separate from iTunes on both Mac and iOS; iTunes is only used for syncing ebooks to iOS devices.