I'm not the sort of person who plays individual games more than once, and not just because I don’t have time for my backlog as it is. I find sticking with a single playthrough is usually the most satisfying option, even if it means missing out on content.
(Insert obvious exception for rogue-likes, or other games where repeated play is inherently important).
There are several reasons to only play once, other than the obvious desire to try something new. There can be good reasons to seek out a more complete experience of a game too, don’t get me wrong, but I'm not sure everyone respects what this risks leaving behind.