The reader being the main character makes the game.  If the reader saw someone else playing the game, the reader would be interested but not interested as actually interacting with the character in the game.  Also, if the reader just read the adventure as a story with the different endings, that would still take away from the interaction experience.  The fact that the reader can make the main character do what they want makes the interactive fiction so much fun and interesting.  It was fun roaming around on a computer game trying to figure out how to get to all of the stages and what to do at each stage.  But with no true ending, I am worried that I may not have really completed the game.  There may be more stages that I have to go to but will never get to because it will take too much time to figure out.  The effect on the reader interacting with this interactive fiction is that they can create their own story through the colossal cave adventure but the downfall may be that they will be unsatisfied if they never reach the ending if there is one.