To answer this question first we have to understand what is AI and further what is an AI experience. AI is a complex field that is involved with the creation of computer systems capable of tasks that were normally associated with human intelligence.
As human cognitive functions are translated into machine capabilities, computers start mimicking human minds, crudely at first but with increasing complexity.
AI experiences are the weaving of these capabilities into applications and interactions embedded in real products and services targeted to human users.
AI has tremendous power and potential but the end recipient is still a human being. If we forget this we run the risk of wasting endless computational energy solving problems that have no desirable outcome for the intended user. User stories, much like in software development, help put the user in the front and center of the process. They remind us to focus on the actual human, his needs, desires, and goals and facilitate them through the power of AI experiences. User stories are the compass guiding this immensely powerful AI machine.