Something I found interesting in comparing the use of a keyboard and the use of a pen is the notion of importance of speed. When typing, most of us would like to increase our WPM. A keyboard which slows us down will not get used much.
On the other hand, in the pen world like on the FPN, "slowing down" or "taking time" are things that are explicitly or implicitly implied. You hear people saying they want to exchange letters because they want to slow down a bit. They want to take the time to enjoy an activity instead of always rushing. Letter exchange is very good for this. For example, I need to find the time to sit down and write the letter. And because I would like to please myself as well as please my recipient, I will take the time to write beautifuly. Then, I need to place a stamp on the envelop and mail it. If I don't have enough stamps handy, I will need to take the letter to the post office.
Then, after a few days or even weeks, depending on where my recipient lives, I will one day open my mailbox and see an envelope and feel a great sense of joy, go home to open it and read the letter. Of course, it will be then time to write back.
Because there is a lot of time involved between the reception of each letter, a lot of things take place in one's life so that when the time to write another letter arrive, one is never short of things to say. Now compare this to e-mail or text messaging. Sometimes, communication become so "easy" that at first, we exchange a lot of e-mails. Then, we start to run out of things to say and eventually, we stop e-mailing.