Why does Mitch Albom, the author, use 3 different storylines to relay the story?

Like in his previous work, Albom imposes a strict structure to his narrative that is just as crucial to the story as the plot itself. He chooses to selectively flash back only to Eddie's previous birthdays in order to develop the character of Eddie, and each of these birthdays highlight someone or something that was very important to Eddie at a certain moment in his life. Additionally, Albom crafts a cause-and-effect seesaw between the past and the present by juxtaposing Eddie at age 83 with Eddie as a child. We learn that although he is alone at the end of his life, there have been many people who have loved Eddie - like his mother and Marguerite - all of whom likely shaped the kind soul that Eddie hides beneath his ornery exterior.