Once again I see people are missing the point. You are not telling a story as you play, you are engaged in events as they occur. And as in real life the outcome of those events is not set. Even when a story uses the present tense the events are set, they are determined. You cannot chage them. A story is deterministic. The events in an RPG session are not determined. By the very nature of the beast they cannot be determined. There are too many variables, too many things that could change the outcome from what is desired to, more often than one would like, something quite undesired.
Yes, people do like to tell stories. No doubt after a good adventure stories will be told of the events. But while the adventure is being played the players are not telling a story, they are, in a very real sense, living the adventure. Stories are experience at a remove, adventures are immediate experience. You could turn an adventure into a story, but it stops being an adventure.
Story: An account of what has happened, regardless of how it is told.
RPG Session: Life in an imaginary world as it happens, for good or ill.