I touched on story before. One of the major parts of it was to give players the ability to write the story. Look at it like reporters. Or bloggers.
You want story in your game. Not everyone will want story in your game, but you will want it there, for the simple purpose to tie it together, to give it coherence and alongside your design documents, an easier to digest feel. Also some players will enjoy reading about it. After all people still read books.
But games are not books.
