It doesn’t really seem like an important one in US culture anymore, thankfully, so much as one of the few remaining fronts on which it is oddly socially acceptable to pester people.
I dunno, maybe it's not as important as it used to be, but high school dances have some cultural heft, and dancing is a centerpiece of the American wedding tradition. Weddings are pretty universally important across cultures. Plus America is becoming more Latino which I understand values dancing pretty highly.
