R2-D2 may be a high-tech astromech droid, but he’s also a lot like a mom of elementary school children. He conveys messages. He holds lightsabers. He basically keeps things safe while everybody else is off having fun.
R2 schleps around a lot of stuff for other people, so why shouldn’t he carry around your deepest thoughts? Or… your grocery list? He can store whatever words you choose to keep inside this little notebook. The plans to the Death Star? No problem! Just jot ’em down right here.