It's impolite to expect to receive gifts.
It's Christmas Day and Billy is with his parents, waiting to open his gifts.
Billy really wants a new bike.
Billy excitedly tells his parents he hopes for a bike but that he will be happy with any other gift.
Billy tells his parents he is sure he will get a bike and will be very angry if he doesn't get one.
Billy gets a bike and his parents are delighted with how happy and grateful he is.
Billy indeed gets a bike but his parents are hurt by how entitled and selfish Billy is.