For your characters to seem real, they've got to have a rounded life and memories must be part of that. Getting your characters to recall things differently (perspective varies) adds depth to fiction and can, of course, add conflict if one insists something happened and another denies that.
Characters who are journalists (to name one example) will shape their stories so how can you show that? How can you show them struggling to not let their bias creep in or are your characters determined to ensure the world sees things the way they do? What happens when someone's memories are trashed? Can memories be stolen (and not just by disease, could someone do it deliberately to destroy someone else?).