In my experience, many of those don't care if they get the absolute latest version. And I can't blame them as many of the "improved" versions tend to come with

In my experience, many of those don't care if they get the absolute latest version. And I can't blame them as many of the "improved" versions tend to come with battery and performance impacts for older devices. I do wish the vendors would keep up with security fixes, though. That's the real problem with Android updating, IMO.