They attempt to be just like normal parents with normal parenting challenges.
No one ever jumps the queue for anything.
They just make a run at fit in."

Royal expert Duncan Larcombe revealed to OK!
(via theMirror) that William and Kate have established a strict rule about attending events with the kids.
Larcombe added: “It was on a school night and they are pretty strict.

The children are in a rather strict regime so that might have been the reason.
However, it seems that they’re focused on protecting them as much as possible during childhood.