There are still friendships that happen solely through the mail. I have a friend who is a pen pal with someone in prison. I don't know too much about prison so

There are still friendships that happen solely through the mail. I have a friend who is a pen pal with someone in prison. I don't know too much about prison so I don't know if there is a reason that theirs is through the mail only instead of using more modern means. Even when I was in school the idea of a pen pal was not foreign (I was in school in the last 9 years. Is that too long ago?).