DRM is not to prevent other files from being readable on the Kindle.
We've known for some time already that Amazon's AZW files are actually Mobi files, but Amazon didn't share Kindle's Mobi PID which would allow one to buy encrypted Mobi books for Kindle.
Think about waiting somewhere in the middle of the day, or perhaps in an airport while you're traveling, and having immediate access to 100,000 books and hundreds of newspapers and periodicals from this pad in your hand.
The Kindle is already able to read more than just Amazon DRMed content, it can handle a number of formats.
A revolutionary portable reader that wirelessly downloads books, newspapers, magazines and blogs to a crisp, high-resolution electronic paper display that looks and reads like real paper, even in bright sunlight.