The Chromecast is Google's fault.
Amazon will only sell the Chromecast if Google allows them to cast to the Chromecast from all of their apps — even on Kindle devices.
Google refuses to allow that, and also refuses to allow Amazon to build their own implementation of the Chromecast library (the Google-supplied one requires Play Services).
The options for Amazon are: remove all Amazon apps from the Kindle, install only Google apps by default, and provide Chromecasting support, or only provide Chromecast supports for users of Google Android, but not those on the Kindle.
This is a clear case of Google abusing its monopoly on Android, and Amazon responding by abusing its monopoly in online retail.
EDIT: This is exactly why I don't use any proprietary IoT devices, but only open products, or things I built myself. Open standards circumvent these entire issues.