I think everyone has missed the point.
What man wants a woman to give him sex because it's her duty? That to me sounds so UNSEXY. If I were a man, I would want a woman that loves sex and wants to pleasure me because it is her DESIRE to do so not because she HAS to. If I were teaching that class, I would instruct the women to explore their own bodies and learn to enjoy the sensation of touch. I would tell them to love their husbands and trust them so completely that giving their bodies to their husband would be easy and not a chore. I think it is a nature tendency for a woman to WANT to please a man, but when you make it an order that has to be followed you take all that away and you create fridged women.