As humans, we can relate much more closely to stories than events. It personalizes them. It allows us to visualize them. All of these things, then, help us to remember these stories and to pass them on. It's why Native American oral history worked so well for thousands of years, and why we teach in the manner we do.
Storytelling is a part of everyone's "human experience". Storytelling dates back to the cavemen, who reenacted hunts for fellow cavemen. Before any sort of writing or printing was invented, story telling was the way the family traditions, histories, lessons, religion, travels, events and many other things were passed down through the ages.
Each person has a story to tell that can somehow relate to another person. When I teach Creative Writing, and we get to the section about story telling, we all sit in a big circle with a large ball of yarn. One person starts and tells a story, then another person, who has a story that somehow connects with the story that was just told (theme, subject, same people, etc) get the ball. This goes on for as long as we have, and by the end, there's a large web, showing how we are all connected by our stories.
When you really connect with someone you've just met, each of you tell stories--things that have happened, funny, serious, or about the same people you know or places you've been. It's a connection between people. The author is using his story, the story of Chris McCandless, and the stories of the people Chris meets to reach out to other people and connect to them, and perhaps, at some point, teach a lesson.