The details in the setting. If the writer knows those little details, then it will make the story richer and fuller. Even if the writer never mentions those details, they will be there subtly.
On the Deluxe Extended version of "Lord of the Rings", there are a lot of documentaries on the making of the film. In particular, the making of the costumes, the set design, and decoration. So much detail went into making the costumes, the sets, the props, real, detail that the viewer never sees, that when you watch the movie on screen the story comes alive. The viewer is transported into Middle Earth, because it looks real.
I am not suggesting that a writer spend an inordinate amount of time on building their world, deciding on the details in the scene or, heaven forbid, dumping it onto the reader. But, if the writer knows some of those details in the background, then it will help build a better story.
Recently, I asked someone where in the world their story was set, because I couldn't tell. They came back with the answer and then said, "It doesn't really matter." No, for that particular story it didn't really matter. And yes, it does matter. The story loses something when the setting is generic. Just as "Lord of the Rings" would have lost something if the costumes hadn't been embroidered, the sword hilts not decorated, the support posts in the Hall not carved.
Before someone decides to counter this, let me say: There will be times when a generic setting is the best setting for the story, but more often than not, it isn't.