What Janni said, plus in books, it's usually what the survivors are dealing with that's important to the story. So yeah, there may be a reason for the death of a character, or not, but it's what those that are left do and how that death drives them that's important. Because they're going to try to make sense of the death, just like we do, and they're going to try to give it meaning, just like we do, and that's usually what drives the plot and character forward.