Google has refused to allow Amazon products to use their apps, like the Chromecast app, despite them being based on Android, and functionally compatible. Amazon does not want to sell products which are explicitly blocked from compatibility with their products. And I'd argue that's a reasonable position.
Being upset about Amazon's response here would be like throwing a fit you couldn't buy a charger for your Chromebook at an Apple Store, it just doesn't make any sense.
Being upset about Amazon's response here would be like throwing a fit you couldn't buy a charger for your Chromebook at an Apple Store, it just doesn't make any sense.