Until recently, I almost never replayed games, but in the last few years I’ve started to more often. Not entirely sure why I’ve had this change of heart, but I know part of it is that my partner loves re-reading books, and that has inspired me to replay games and see what a fresh perspective brings to them.
I’d say there are several reasons I’ll go back to replay a game:
It’s an old favorite / classic
I recently replayed Link’s Awakening and am in the midst of replaying Pokemon Silver (by way of the SoulSilver remake). For these kind of games I’m replaying them partly for the comfort food / nostalgia factor, and partly to try to see them with fresh eyes and notice things I didn’t years ago when I first played them.
There is new content, or content I missed
A lot of more recent games have substantial “post-game” content or DLC, so I’ve found myself going back to games after reaching a stopping point and putting them down for months. For me this is the Celeste B-Sides, or unlocking new mechs in Into the Breach, or doing the DLC shrines in Breath of the Wild. To me this still feels like “replaying” even though the content is all new, probably due to the familiarity of the controls, mechanics, and world. I think this is a lot like what @Alveric is talking about.
To share a game with someone else
I’ll replay a game to share it with my partner, or if my partner wants to share one with me that I haven’t played. We’ve played Minish Cap and Toy Story 2: Buzz Lightyear to the Rescue for that reason. We are thinking of playing the Harry Potter and the Chamber of Secrets game soon, which my partner hasn’t played before. Often these are games that are nostalgic to one of us, so it’s similar to the motivation behind the “old favorite” category. But there is something distinctly special about getting to see something you enjoyed being experienced for the first time by someone else!
It’s a ritual / tradition
Last year my partner and I replayed Night in the Woods to mark the onset of fall, and I think it’s likely we’ll do it again this year. This is the only game playing ritual I have, but it was pretty great and I kind of wish I had more like the ones several folks have mentioned earlier in the thread.
Anyway, replaying games is new to me in the past few years, but I feel like I’ve been getting a lot out of it so far!