Do the majority of customers even care if they have the latest version? Heck even on iOS, I don't recall the last time anyone outside tech even discussed the version of the OS. Pretty much in line with my experience of what happens on the desktop.

That’s probably because it’s trivial for people to update iOS, making it a non-issue.

New iPhones don’t come with iOS 8 or 9 (let alone 5). Worst case is 10 because it was manufactured before 11 released.

And people do care. That’s how you get some new features like new Emoji or the upcoming Apple Pay for iMessage.