I've iPhone user I've ever met outside tech circles avoids installing OS updates. They end up updating soon anyway for a variety of reasons (some updated apps stop working, update occurs "on its own" overnight, to get rid of of the notification icon, and so on).
It does help that the process is pretty painless. And at least for me, a good excuse to do a reboot - which I really do as seldom as possible on my laptop and iphone.
