I’m sure that one of Google’s OKRs is to increase the number of pure Android users. This has multiple benefits: users get the latest updates faster, Google promotes its own apps, users get to try Google’s original flavor of Android, the latest version of Android gets more market share and developers are encouraged to use the latest APIs.
Here are some strategies used by Google to make pure Android (or almost-pure Android) more popular:
1. Nexus is now a family of affordable devices and Nexus 7 is the most popular Nexus device ever released. Google sells them online in a few countries and provides software updates.
2. Google Editions of the most popular Android devices: HTC One and Samsung Galaxy S4. Manufacturers provide software updates for the devices and include some of their software. Devices are still sold online via Google Play, but only in the US. Maybe other devices will follow.