The protocol of the British royal family is very strict and makes no exceptions for anyone. Even such a prominent figure as Kate Middleton is subject to difficult constraints. In some places, the rules reach the point of absurdity.
The Duchess’s three children from Prince William turned out to be “more worthy” than their mother, and therefore Kate is obliged to show them signs of respect. Middleton can not do this only when her husband is next to her – says the royal protocol.