It isn't unique to the Sussexes that they leave their child behind when visiting another continent.
However, it was more the Queen's generation who did this. Prince Charles and Princess Diana took their children with them. The Cambridges did, too.
And anyway - I thought that M and H wanted to break free from so-called royal tradition. Or should that be Royal Tradition?
Isn't that the raison d'etre for SussexNotRoyal?