I don't know about the internal structure of Apple vs. Android handset manifacturers, but from the outside, they seem to treat their respective OSes very differ

I don't know about the internal structure of Apple vs. Android handset manifacturers, but from the outside, they seem to treat their respective OSes very differently. Apple treats iOS the same as Mac OS: It will run on any compatible device that meets the minimum requirements. For Android handset makers, they treat Android as the firmware for the device they are making. When they start on the firmware, they take the version of Android that they want, write the HAL, and then add their special stuff plus any carrier related crap they've agreed to. Once you're not selling that device any more, why would you bother to update the firmware? Users (and maybe Google) want to Android to be like iOS, but the handset makers are treating it the same way they treated their old internal phone OSes.