They do. Or at least, they did. Well, sort-of, in the sense that it was still Linux. The e-ink kindles - at least the first several generations, I have no idea about the recent ones - were a pretty vanilla Linux with a java userspace managing the UI - but NOT android. The original Echo seems to use a version of the e-ink Kindle's OS, while newer Echos use FireOS aka Amazon's android fork.
Amazon really tried to make FireOS work as a google-free mobile OS, but just never got the volume. Ok, I guess they still sell those $50 tablets or whatever, but millions of Firedroid devices is still a rounding error compared to billions of Google Playdroid devices, or even hundreds of millions of Baidroid devices. Network effects dominate - even Apple has a hard time with maps for exactly this reason.
Amazon really tried to make FireOS work as a google-free mobile OS, but just never got the volume. Ok, I guess they still sell those $50 tablets or whatever, but millions of Firedroid devices is still a rounding error compared to billions of Google Playdroid devices, or even hundreds of millions of Baidroid devices. Network effects dominate - even Apple has a hard time with maps for exactly this reason.