Just a guess, but I imagine that it moves certain people because it represents lost innocence.
Screw the stupid story in the link. People here were commenting before the link was presented. In this drawing, Charlie Brown has grown up. He has his familiar football, and his faithful dog Snoopy with him. All the bullying he took as a child has made him tough enough to survive in a hostile land. Thoughts of Peggy Jean are distant and infrequent memories, supplanted by more pressing thoughts of making it through another day.
Childhood shows the man, as morning shows the day.
