Why does Krakauer devote Chapter 14 and 15 to his own story?

In Chapters 14 and 15, Krakauer, himself, becomes a character in the novel. He is no longer just narrator, investigator and interviewer, as in telling his own story, he illuminates a the parallels between himself and McCandless, which serves to help us understand that he understands Chris and his motivations because of his own experiences.