I think that declining ability in cursive might be better explained as a matter of writers’ lack of interest in, or lack of care for, the handwritten word.
“Years ago, years and years and years ago, my children would occasionally spend a morning on campus with me on days off from school. On one such occasion, my son Ben labeled a poster of Thelonious Monk in my office.”
From the Smithsonian’s Archives of American Art: The Art of Handwriting. The online version of the exhibit has handwritten letters and postcards from thirty-nine artists.
“I’ve come to the conclusion that handwriting is good for us. It involves us in a relationship with the written word that is sensuous, immediate and individual.”
A look at life at the U.S. Postal Service’s Remote Encoding Center, “a room where hundreds of clerks sit in silence, day and night, staring at America's worst-addressed envelopes.”