Dumbledore:

"And his knowledge remained woefully incomplete, Harry! That which Voldemort does not value, he takes no trouble to comprehend. Of house-elves and children's tales, of love, loyalty and innocence, Voldemort knows and understands nothing. Nothing.

That they all have a power beyond his own, a power beyond the reach of any magic, is a truth he has never grasped."

- Harry Potter and the Deathly Hallows, J.K. Rowling