Some people are more talented than others. If I take my time and especially if I have lines to guide me my cursive is legible but certainly not pretty. In grade school my handwriting grades were C's, I just couldn't do any better. I'm also horrible at drawing, even my drafting is messy. Just no talent whatsoever with my hands.
It is sometimes very difficult for me to read what a census taker has written in 1850 ... but, I have been able to read somethings written by the "founding fathers."
Steve, my thoughts on this is a big part the ability and talent of the author but also the speed at which it was written. If I'm in a hurry my cursive handwriting is atrocious. If I take my time it's still not good but at least legible. And part of it follows from what Pulsegleaner said, some people take more pride in their handwriting than others.
My training in the army was as an 05-C, radio teletype operator, which I never used on active duty. The minimum requirement for Morse Code was 40 words per minute, a word was combination of 5 letters or numbers. They not only required that you print instead of using cursive, they taught you how to form certain letters and numbers so they would be more legible when written faster. Capitol case of course, no small case. Some of the ways to make those letters was different from how I was taught to make them in my drafting class. In drafting and code taking, you print, you don't use cursive.
It's been many decades since I used Morse Code. I think it would come back relatively quickly if I tried but I really don't have the desire.
To demonstrate how bad my abilities are I'll tell a story on myself. When I was in college taking the engineering drafting class we had a thing called the military draft. Yeah, I'm that old. If you met certain requirements you could get a student deferment and not be drafted. My drafting instructor asked me if I needed to pass his course to maintain my student deferment. I told him yes, which was actually true. So I got a D instead of an F. I said my drafting was messy.