It might not be "supported", but I thought you could easily sideload play store and play services? You don't even need to muck around with rooting or even adb.

> Amazon's devices don't support the Google Play store...

FireOS devices aren't certified by Google and so, they do not come with "Gapps" (including the Play Store) preinstalled. Even if they were, Amazon might have some reservations about preinstalling Gapps (which run with higher than normal privileges), effectively letting Google get hands on its user's purchasing habits.

All that to say, this is a business limitation not a technical one.

See also: Google's iron grip on Android: Controlling open source by any means necessary, https://news.ycombinator.com/item?id=6582494 (2014).

I have two Kindle Fire tablets (they're low-quality as general purpose tablets, but cheap and good for reading comics or books) and both have Google Play on them.

Mind you, I had to sideload it for both of them.