Honest question - What do you see about it as being useful? I was taught to write in cursive when I was younger but I honestly don’t feel like it has ever been all that useful (especially given that most of my communication and writing is done on a computer/smartphone).
Anyway back to the point, cursive - or "joined up writing" as we call it - is used by most people into adulthood even though nobody uses fountain pens past primary school because it is quicker than printing.
I later retried using a fountain pen in university under the assumption that perhaps I've used too much force or I was using low-quality pens, but the result was still the same, minus the bent tip perhaps. Good riddance!
As a kid it's kind of fun to get your hands dirty with ink, even fighting with cartridges (pressing them like toothpaste tubes and the like).
Recently I designed a blotter and started selling it on Amazon (Europe) this month; it's a completely niche product but it's selling a little nonetheless, meaning there's some demand for it.
It's not a panacea in France though, since people usually buy their kids cheap ones which leave a lasting bad impression. Many people get very defensive about handwriting and that is partly accountable to the terrible fountain pens they had to learn with.
Err, there exist erasable ball-point pens too, such as Pilot's Frixion line.
They don't teach you how to use one - to me, it's always been the same thing as using a ball pen, except you trade the convenience (you have to change the ink cartridge) for practicality (you can erase the ink with special eraser) while keeping some style (it's still ink, not pencil, kept for drawing).
Getting a new pen felt weird at first, but just like a new pair of shoes, you end up accustomed to it.
So it's interesting to read about fountain pens in America, where people talk about having to "learn" how to write with a fountain pain. It's seen as such a special, luxury or just nerd thing, while in France, it's just something common nobody really pay attention to.