Apple’s modus operandi has always been to funnel all transactions taking place on their mobile devices (iPods, iPhones, and iPads) through their own merchant account.
This has been nothing but distressing to every other seller, especially e-bookstores and periodicals. It’s not just about the money and the cut Apple takes. It’s also about Apple holding on to the data acquired – so Amazon can’t mine the data acquired through your purchases through apple for their own marketing (though Apple can and does use that data).
So, virtually every major e-book retailer has changed their iPhone and iPad app so that you can’t purchase directly. This includes the Kindle, Nook, and Kobo. The GoogleBooks app is just gone.
By changing the way their app works, they will lose some spur of the moment sales, but will be able to keep the data and not pay Apple a middleman fee.