Right, and they do. But if I buy an eBook from Amazon, or I buy a physical book from Amazon, what is the difference in the services that Apple is providing, tha

Right, and they do. But if I buy an eBook from Amazon, or I buy a physical book from Amazon, what is the difference in the services that Apple is providing, that explains why Apple wants their cut of the eBook but don't want their cut of the physical book?