The Kindle Fire tablets are also designed to sell Amazon content, but they benefit the customer with their rock-bottom pricing which the Fire Phone did not have.
I have one of the original Fire tablets, and would not buy another one if not for the express purpose of delivering Amazon content - videos in that case, since the actual reading experience is far superior on a real Kindle. It's not a bad tablet, but not having the Google apps, as well as something relatively close to stock Android, makes it not as useful as it could have been.
They also benefit from the fact that tablets (at least in my experience) are primarily content consumption devices, whether that's books, videos, or games.
