I occasionally see discussions about this when talking about writing fantasy. The idea that a magic system in a story should have spells and other elements to it that might not necessarily be relevant to the story, but are put in order to have the worldbuilding feel more "natural" and "lived in".
On the other side of the spectrum I see some people say that the only magical elements that should exist/be mentioned in your story should only be stuff that's immediately relevant to the story. Basically the spells are just different devices used to advance the plot or to make something in your story happen without it being a plot hole.
Where do you think the Nasuverse falls on this spectrum? I'd it's mostly the former with some smaller things just existing to facilitate the story or shoehorn fanservice like pseudo-servants.