Hmm.

I think that there are a couple of ways to look at this.

First, there's just casually looking over someone's shoulder.

I haven't done this for many years now, but I don't enjoy playing jumpscare games -- don't enjoy being startled -- but I don't mind watching someone else play one, can enjoy the story.

I was, years back, at least okay at FPSes, but never outstanding. I had a friend who was really solid and didn't mind having people side-seat driving, and I enjoyed that.

Second, there's outright collaborative play, but where one person has the controls. I think that this often comes up a fair bit with adventure games -- I read about a number of guys talk about playing a game with their wife, but where they're doing the clicking. Adventure games aren't much about the control, but figuring things out and experiencing the story. I think that the experience watching and thinking it through here can be pretty comparable to playing. Maybe more fun if there are some tedious bits that you can just skip.

Third, there are professional streamers. That's a whole 'nother ball of wax.

Cataclysm: Dark Days has some streamers like Vormithrax that amount to being the tutorial to the game for many players, because it's so stupendously complicated and ever-changing, and he verbally walks through what he's doing.

There are e-sports players. I don't really like playing Starcraft or DoTA 2 multiplayer, but I can enjoy watching a presented event.

I understand that there are some "gamer girl" streamers; obviously there are people who enjoy that. I've never looked into it, but I imagine that it could be entertaining in a way that the game alone isn't.

I remember once watching a fighter pilot watch an arcade-ish air combat game (IIRC either something in the Ace Combat or Project Wingman series). They were commenting on tactics, realism, and plane capabilities. Again, interesting in a way that the game itself isn't.