Loki seeks a woman to satisfy those needs of the physical sort. He cannot satisfy himself fully with that of an Asgardian woman. He does not crave to be dominated, he does not want an equal match in physicality. No, Loki wants a woman that will subjugate to him, and only him. Loki wants a woman to rule, to own, to ruin. He can only find her on the feeble planet... On Earth.