Its more like older generations of all sorts nailed cursive. Remember, back then 99% of all writing was handwriting. Even those who had typewriters only used them to make final drafts of documents - the first versions were all handwritten. The fact that people's handwriting back then was so good comes from them having ample opportunity to practice good handwriting.

I actually grew up there, and I remember that my teacher's would take points off for anything less than awesome handwriting. During math exams we'd basically do all the work on a separate sheet/scratch sheet and then copy it over to the final notebook we'd submit for grading. Great handwriting and neat notes were considered a sign of an educated person... (With the exception of doctors, they were required to have crazy handwriting, at least for prescriptions)