This is why.
Writing by hand takes time and effort and purposeful thought. As opposed to a conversation quickly forgotten, a note lasts forever. And different from a text message that can be forwarded or mass-produced, a handwritten note is for one audience only. It’s personal, delivered into one set of hands from yours.
Because you can re-read a text you send, the message becomes something you share with the receiver. It belongs to both of you, and it’s impersonal in that way. But a note belongs only to the receiver. After a time, you (the writer) forget what you wrote, but the receiver never forgets what he or she reads and what he can continue to re-read at any time. Your words belong to him only, a precious gift, a secret between the past you and present him.
A handwritten note is like a time capsule. It’s a treasure chest that only one can open. It’s beautiful, it’s rare, and I hope it never dies.