Of course, the most critical part of postcards and letters are: a proper address to send it to, and a friend to write.
Also, I like to think about all the hands which touch the card as it makes the journey from my writing desk to a happy (I expect) recipient who peeks in their post box / letter slot and see something other than a utility bill or an bulk/junk mail from a real estate agent.
I also wonder how the “hand off“ in international mail works from one country to the next. Do the workers peek at the – almost illegible – scribble on my postcards? Do they wonder who wrote the missives and who the recipient is? . Do you think about these logistics & vagaries? Or is it just me? .