I got into fountain pens because at one point, I was fully relying on computers to do my writing for me. Autocorrect and all that good stuff, and not to mention that I had hideous writing.
So for me, it wasn't about just making my handwriting quality better, but it was for improving almost every aspect with the way I compose my words onto paper.
I found my Grandpa's Underwood typewriter a while before I got into FP's, and I used that to train myself too, in typing and how I compose things. (Not music compose by the way!) I am still learning tons about how I write and how I can improve it. I'm 18 now and it is a shame that I didn't get into it when I was much younger--say 9 - 10. I got into it when I was 14.
If this was about typewriters, then it would be to improve my typing and technicalities, and because of someone close to me. I bet Gramps is happy up there seeing that his beloved typewriter is being used all the time, and being taken care of!
And to think of it; if I hadn't discovered my soft spot for fountain pens and typewriters, I would not be writing novels right now, or short stories that would become word of the school! Those ways of writing bring out the best, and the most authenticity of what you do with your writing.
My reasons are a bit more serious, as you can see!