There was an enormous volume of material that I never understood in high school because at the time I either didn't care or other things seemed more important -- my mom was dying, for starters.
But just having exposure to that material planted it in my mind and, in many cases, I revisited those topics later as an adult and learned them properly.
To be clear, I am not advocating for doing away with testing or schooling altogether. I am only pushing back on the idea that a 16 year old who doesn't care about cursive or calculus or Chaucer or whatever today won't ever care about those topics unless we mandate he pass an exam or course on it.
More broadly, my point is that there is a cost to "forcing them" as the grandparent advocates with regard to learning cursive. The moment you "force them" you also guarantee that some people won't graduate because of that extra requirement. There are other ways to enrich people's lives without force feeding, e.g., mention it and devote a question on an exam to it.