The eBook Reader blog wonders:

Kindle ereaders are one of the few reading devices on the planet that don’t support ePub format.

Kindles are the most popular dedicated readers and ePub is the most common ebook format, so what gives?

Why doesn’t Amazon add support for ePub ebooks to Kindles?

I guess this could be a rhetorical question, but the answer is ridiculously obvious: because Amazon doesn't want to open its system up or allow people to read e-books that they've bought in other places. If you're buying an Amazon e-reader, you're buying into Amazon's system. That deal is never, ever, ever going to change. If you expect Amazon to open their system up because it's the right thing to do, or because their customers would prefer to have one e-book library rather than a confusing mess of proprietary formats, you're going to be waiting for a very long time. It'll never happen.