Re: Scratching my head
I think there is some justification - in that phone chipsets aren't standardised in the way that PC architecture has been. Which means that it might be more work for the phone manufacturer than just, get Google's latest version of Android and apply to whatever skin/launcher they've put on the thing.
I could be wrong here, but I understand that sometimes the OEMs may need software updates from the chip manufacturers - that they're also not doing. Although if they had the will, they are the customer so could have put it into their contracts - or paid for after-sales service.
Obviously it would be even simpler had Google refused to allow all the vendor customisation (or usually buggering up) of Android - so they didn't have the excuse of not having the resources to apply the patches to the crapware they'd already dropped on their phones. Alternatively Google could just have forced vendors who customised to guarantee 4 years of patching, or no Google Services for them. But Google's record on supporting their own hardware is only about 2-3 years, so they're not exactly paragons of virtue here. Let alone the shit they get up to with end-of-lifeing their IoT stuff.
Google decided to take the easy route and partially get round the problem by shoving increasing amounts of the functionality into Google Play Services. This has the twin advantage that they control the updates, so at least your Chrome browser and other Google apps are up-to-date. And also that Google now have more control of Android, because the open source bits don't have Google Play Sservices - and it's therefore much less valuable without Google. As Huawei may find trying to sell phones into Western markets - obviously de-Googleified Android dominates the Chinese market.