I'm no expert, but this is my impression based on seeing and using lots of nibs :): Most drawing / calligraphy nibs only work well when you're pulling the pen

I'm no expert, but this is my impression based on seeing and using lots of nibs :): Most drawing / calligraphy nibs only work well when you're pulling the pen (e.g. try pushing with a pointed nib, and you'll quickly tear up the paper or break the nib). Because of this, they can be of fairly simple construction, made of flat uniformly thin metal (generally just steel AFAICT). As they're relatively cheap and easily replaceable, it's not a huge deal if a nib breaks, you just put in a new one, and you're not out too much money. Fountain pens, on the other hand, have to work reasonably well when pushing the pen too, so you can't really make them entirely out of thin flexible metal. Together with a more complex ink delivery mechanism, the nibs seem inherently more expensive, and so tend to be part of the pen rather than a disposable part (I imagine the average person who just wants to write his stuff wouldn't be very happy if they had to constantly replace the nib either). By making them out of relatively stiff metal, you can sort of avoid some of the problems while still using cheapish construction. I don't know why gold is better offhand, but I imagine it may be better able to put up with the forces involved when the nib is thinner and more fleixble, without breaking.