Fountain pens provide a feel
The feel of a fountain pen when writing is not unlike turning. As I feel my way across a piece of wood with a really sharp tool, as the barrel takes shape and cuts clean, I feel a palpable sense of connection to the wood. I can tell where the wood is soft or gnarly. With a fountain pen against a piece of paper, I can feel the words take shape. If I try to write with too much passion, the pen slows me down. If I take to much time, the pen flows ink into pools on the paper.
I can make pens that write just fine, but if i take the time to craft a pen, the reward is much more than a tool, its a treasure. The same goes for using a fountain pen, if all you want is a tool, any old pen will do. But if you want a treasure, a fountain pen is the careful crafter's choice.