There's often a skill that seem interesting, but I can't see doing anything for me in my day-to-day life. What have you learned that was a lot more effort than the payoff was worth?
It was already going out of fashion in schools when I was growing up, and people did not like it when a teacher (usually older) made them practice it. The original argument of it being faster didn't apply once computers became common in schools/homes, and printed letters (writing like a typewriter) are better for clarity.
However, I think there is value to it when framed as an artistic skill. Calligraphy strengthens motor skills, and if you make the lesson less rigid then kids can have fun with it and figure out how to express themselves.