royalty humility

Been watching some old fairy tales, and noticed a theme; that the royal main character has a humble upbringing: snow white was treated as a low class servant despite being princess. Aurora was raised in the forest by fairies to hide her royalness. Cinderella was raised as a low class servant despite being at least nobility. They also can all talk to birds.... But I digress. 

I wonder at why this permeates the European folklore.