Apple’s in-app purchase policy

I read today that Amazon finally caved to Apple’s in-app purchase policy. I can understand Apple’s desire to get its cut, but the desire to enforce this policy puts an unnecessary burden on customers and creates usability issues that are extremely annoying. For instance:

Right now, if I want to buy a book from the Kindle app on my iPad, I can click the Kindle Store button and it will open a web browser to the Amazon Kindle site so that I can make my purchase. If I decide to upgrade to the latest version of the tool, the button will no longer exist, meaning that I will have to navigate to Safari, and then navigate Amazon. This adds two additional steps to a process that was almost as efficient as you can get. Adding steps to a process? Really?

This might be good for Apple’s bottom line, but I have a question for Apple: how it this useful to consumers?