There's no good business reason for Amazon to play nice with everyone else and many good ones for them to continue with their proprietary format. Especially while they continue to offer the best eReader hardware that is available.

In addition, it guarantees people will purchase their books for their device in their store and not someone else's. Why wouldn't they?

Considering they have free 3G access anywhere in the world with a Kindle, I've had nothing but convenience with it.