One of my least favorite memories of the military was mail call on Sundays. A room full of people, all excited to get mail from all their friends and family, girlfriends and wives. and me, getting nothing. I had to sit there twiddling my thumbs for hours waiting for it to be over.
If you have friends in prison or in the military, it means a lot to them to visit them, send them a letter, or if in prison, buy them some food or send them some money to make life less miserable and lonely.