One of the few complaints I hear about the Apple experience is the requirement to install iTunes on a computer in order to 'activate' their hardware products. That's very telling. Why does a company famous for perfecting the user experience create this roadblock for its users?
It is to convert iX(Phone/Pod/Pad) users into iTunes users. You have a revenue stream from iX user for maybe 2 or 3 years . . but you've captured an iTunes user potentially for decades.
It's been a long term plan. I remember nearly a decade ago when Apple broke their iPod so that MP3 files couldn't be transferred onto it using the standard USB mechanism. It was no longer an MP3 player - it was a portable iTunes player.
The goal is no less than to acquire 30% of the price of every movie, TV show, book, game or any other digital product sold and to make them profitable long after they've stopped innovating.