There are five models of Kindle: The Kindle, Kindle Touch, Kindle Keyboard, Kindle DX, and Kindle Fire.
Only 2 of them matter: the Touch and the Fire.
So why the other models?
The Kindle Keyboard and the Kindle DX
I think these are still for sale because they are still in stock.
That family-of-Kindles banner that is on top of all the Kindle pages does not list the DX.
And if you go to the Kindle DX’s product page it is now outdated. The page doesn’t have the top banner showing the other Kindles, and in the table comparing all the Kindles only the past models are shown with their old names.
Surely it’s only a matter of time until the Kindle Keyboard and the Kindle DX are discontinued altogether. (Perhaps once the Kindle Touch or Kindle Fire start shipping?)
The plain Kindle
I think the “plain” Kindle — one with the 5-way controller — is in the product lineup primarily to help boost sales of the Kindle Touch.
If you’ve ever read about the paradox of choice, you’ve probably heard the wine theory. The idea is that someone is ordering wine at a restaurant and there are three options — an $8 glass, a $10 glass, and a $20 glass — they will most-likely pick the middle option.
The $8 glass causes the $10 glass to seem like a much better value.
Likewise with the Kindle and the Kindle Touch. The plain Kindle causes the Kindle Touch to seem like a much better value.
Why buy a Kindle that has a shorter battery life, less storage, and no touch screen, when you can upgrade to something with double the battery, double the storage, and a multi-touch screen for just $20 bucks?