In chapter 1 of Juul's book, he implies that when it comes to games the rules are more important than the fictional aspects. I respect his opinion, but I feel that fiction plays a bigger role in games than he thinks.
The best example for this is the new DmC: Devil May Cry game from Capcom and Ninja Theory. It is a re-telling of the story from the original Devil May Cry series, but with some major changes in the story itself and the characters. The rules of the game have relatively stayed the same; use the character to traverse paths that lead to a set goal in a level while encountering and defeating enemies. The final results are either winning or losing. The rules that define the combat system in the game act as the foundation, but the flair of the actual combat draws in the gamer to keep playing.
The reason I mention the new looks of the characters and the flashy fighting, in my opinion, is that they provide amusing gameplay and acts as a hook for possible buyers. From a economic point of view the gaming market relies on the fiction of games to sell and make profits. To a gamer, like myself, I enjoy to see what worlds and characters are developed and how stories progress, like in DmC or Kingdom Hearts.
There are games that, as Juul mentions, have rules and no fiction that are still successful. Games like Tetris and Pong are great examples of games void of fiction but are still successful. If a DmC programer tried to apply the rules of the combat with no fiction (or more accurately described "flair") than the game would be very unsuccessful.