It's one of human natures need. (food, sleep, and sex) Yep it was built into us. However it is to be between husband and wife. Satan knows this and knows it's a big weakness especially for men. If you think about it IF you knew your enemies weeknesses wouldn't you exploit them?
We ea. have our own weeknesses and he KNOWS what they are. He will exploit them at all cost to get us to sin.
Satan's NO.1 goal is to keep people from God.
I agree with it being a need along with food and sleep...because without it we would not survive.
It being between "husbands and wives" is a man-made belief and should not be bunched in with human nature.
But a weakness, I don't follow you here?
How would that keep somone from God?