Hades is a neat counterexample, at least in the mainline plot — you’re doing your thing for personal, even selfish reasons. It does get recontextualized later on, though, and I think that recontextualization speaks to why games are this way.

Depending on what you want to focus on, a game can only accomplish so much, and RPGs, which are typically focused on the journey of just a few characters, need to make sacrifices to focus on those characters. Aside from the most wild developer fantasies, you can’t really simulate a whole living world and tell deeply personal stories and have engaging minute-to-minute gameplay. So with RPGs, where the mechanics are kind of innately focused on just a few characters, the narrative also kind of has to focus on those characers. It just leads to a more developable game, more intertwining between mechanics and narrative. Otherwise you’re spending all this time with faceless stat blocks.

In Hades, the core gameplay loop stays pretty much the same, but the reasons you’re doing it changes — that allows the developer to fit a whole lot of narrative in the flow of the game while reusing that core gameplay loop. It’s the same in GTA: you do the same driving and shooting, but for different reasons. GTA especially does a lot with the quest-giver role, where a slight variation on a street race would be a lot more boring without Brucie’s roided-out bellowing, and that sort of benefit is where the quest-giver role shines. The narrative of your characters intertwines with someone else, you get a bunch of (hopefully) good voice acting and writing, you see a new side to your protagonists, and the plot or mechanics can advance.

The quest-giver role is just too powerful a narrative tool for designers to ignore most of the time. It lets you put all these things that a game is made of into one place and make them work together.