In the age of electronic communication, email, IM, DM, chat, it's rare to receive a handwritten note in the mail. There are few things however that express that you care enough about someone to spend the time not only selecting beautiful paper or a pretty card but also that you took the time to handwrite it.
"A sealed envelope captures the moment in time that you thought of your friend, acquaintance, love and sat down to share your gratitude. We live in an impersonal world. Phone calls end, emails disappear, texts drop spare change compared to the riches of sending stationery, ink, signature, and a piece of your time they can hold and read and read again."