They do not have responsibility.
They do not understand sin.
Pen is lifted from their shoulders.
They do not understand the dirty things of this world.
They have not lost their natural disposition through sinning.
They do not understand gender differences and sex.
They do not have jealousy, hatred, and other ill feelings.
They do not have to fight their lower self.
They have no worries except for playing.
They possess the simplicity, which we have lost after growing up.
They exude innocence.
My dua for every Muslim child:
O Allah! Keep our children away from sin, disobedience, transgression, shamelessness, and all the ugliness of this world, and keep them upright upon their fitrah and make them grow upon guidance.