The most important element in the book is the dialogue between Mitch and Morrie. The advice that Morrie tells Mitch is the part of the book that sticks with the reader. Many of his quotes on how to live life and not take anything for granted are pieces of information that any reader can somehow relate to.
Morrie's little aphorisms give the audience something to connect to and make the story universal to all readers. Without his direct quotes, the audience would not reach the same emotional level that the story is so famous for.