When I was in the US in December, I wrote letters by hand to people I had not seen in sometime. I am still thinking about it.

These are some possible reasons why it was meaningful:

It reminded me of being a child and writing letters to people.
Holding words of affection in my hands, that someone bothered to sit down and write, carries special weight.
It is a way of being present without being present in the room.
It demonstrates a literal amount of time, documented, thinking about another person.
It required me to consider that my lack of living in the US impacts people I know who live there. It give me some awareness.
Letters are symbols that last a time. They don´t evaporate like an email or a text. They stay with us.