When you tell someone a story in person, you probably know the person
you’re talking to. You will at least have a rough idea of how familiar they are
with the people and places you’re referring to. And if you misjudge, they can
always ask you questions.
In fiction, it’s much harder to know exactly how much information a
reader needs or wants. And even if you did, it would be impossible to provide
since you’ll have more than one reader, and each will have different
requirements.
You can’t get the balance right, because there is no way to please
everyone.
However, that doesn’t mean you can’t get it wrong. You may not be able
to please all the people all the time, but you can certainly piss them all off.