Because I think that at some point we're going to come to a point of convergence where people don't want 50 devices to do 50 different things.
If you could get a tablet for roughly double the price of the Kindle (who knows how accurate that statement is but I'm guessing it'll have to be cheaper than your average macbook) that was full color, allowed you to be able to watch HD video content, surf the web, write emails, take notes, take care of all of your scheduling, manage your music library and a whole host of other things why would you buy the Kindle? Most folks that I've come into contact with are pretty ok using their iPhone as a reader so I'm betting e-ink isn't turning out to be the advantage that the ebook man'f thought it would be.