Because then it would be trivial for you to also read books that you *didn't* get from Amazon. And we can't have that, now can we?
No, not for a $50 device that they are probably taking a loss on. It sounds like you think you are either entitled to take advantage of them, or else are smarter than them. You want a general use device? Pay for it. You have 100GB of books? Unless you are a public library, the odds are that they are pirated. I'm not defending the current corporate owned cultural system that we have gotten ourselves into, but yeah. They locked out the card. Go buy an iPad.