It seems true that the labels required this; and it was just serendipitous for Apple that it locked-in users. Although... Amazon dropped the DRM a year earlier (it seems). So it sounds like Apple exploited this good fortune to the hilt, and then some...

It reminds me of how Apple forbids Flash - it's true that flash runs very slowly on mobile hardware; and also that most flash applications are designed for the mouse and don't work ideally with multi-touch; and that this runs counter to Apple's focus on the consumer experience. It's just serendipitous that this leads developers to create exclusive content for iOS, and gain expertise in iOS and Apple's toolchain, which also have sticky qualities (they take effort to learn, and it's not transferable to other platforms).

New products often have natural competitive advantage in many different aspects. It's up to you to find them. It's not something you can just make up for the purposes of having a competitive advantage because if you can't "blame" some real factor for it, customers will hate you for it. So, just recognize those competitive advantages, and don't stuff them up.

Perhaps one approach is to look for possible competitive advantages, and ask if any of them will also happen to give some great benefit to users, that they value.