Wow, don't they look like they are having a ball. I don't think I have ever seen the Emperor with a smile let alone absolutely beaming at his wife. What is more, they were so light-footed and at ease as they moved around the floor, it was easy to see they were enjoying themselves. It spoke volumes about how often they do in fact, dance.
As to the younger generation, I think dancing is a compulsory subject for all of them, as is the art of making polite conversation. If they debut around eighteen they are expected to dance and make small talk with total strangers.
Somehow I don't think their royal parents subscribe to the old 'chuck 'em in the deep end' School of Dance, after all, who would want their guests sitting beside an inarticulate and socially ignorant young royal and having them dance with someone who only learned the box step for the waltz last week. It would be so utterly mortifying that they would never want to do it again which would be totally counter-productive.
Turning out well-rounded and "finished" young royals, equally at ease in State Dining Rooms and Ballrooms would be a must. Just look at the Swedish debuts at the Nobels, smiling and chatting away and looking quite animated.