I'd say this is one of the things Apple has been very successful at. Releasing a new version of iOS has become a highly anticipated event for a staggeringly large portion of the user base. From the way they handle updates on a software level (auto-updates and persistent notifications) and on a social level (turning it into a large PR event tied to their new generation of devices). It's something Google was never able to do, and I don't think it's any accident that Android updates are lagging so badly.

I think there'd be a veritable shitstorm if, say, AT&T suddenly decided to withhold iOS 13 for 6-12 months, while it's effectively SOP for Android devices (where you have manufacturers needing months to release a new version, then providers who delay it even further to test ... something).