Here's why:
* "Auto" means "self": The prefix "auto" in autobiography signifies that the story is about the author themselves.
* First-hand experience: Autobiographies are written from the perspective of the individual who lived the events being described. They share their unique experiences, thoughts, and feelings.
Of course, someone else might help with the writing process, such as an editor or ghostwriter. But the core content and perspective of an autobiography always come from the person whose life story it is.