It kind of is Google's fault. Most people associate any version of Android with Google. Manufactures that don't update their phones causes harm to both the manufacture's image and Google image.
Personally, I place all the blame on Google for not making the upgrades possible from their side. It should be easy to upgrade the core operating system as easy as updating Windows, OSX, and Linux.
Personally, I place all the blame on Google for not making the upgrades possible from their side. It should be easy to upgrade the core operating system as easy as updating Windows, OSX, and Linux.