They had chasitity belts in the old days too, though typically they were for chronic masturbating boys (horsehair shorts? oooh!). Female chastity belts are older (1500's and such). There is actually a museum in Europe that showcases chastity belts over time.
For some men, they like the thought of having their cock locked up and out of their control. I'm sure you know of the influence the little head has over the big one!
So for those who are into chastity, its another way of being constantly controlled and dominated by someone else. Most male tops aren't interested in denying sex to their female bottoms. Plus I think there is a connection in women where after an orgasm chemicals and hormones in their body are released that actually enhance their feelings towards their lover. I could be wrong there but I recall something like that.
Chastity can come in many flavors. You might find that you would like enjoying your man on Monday, and after you've had your wicked way with him, putting his chastity device on, locking it, and with a gleam in your eye say "I'll see you on Wednesday sweetie" and send him out the door. It could definitely lead to an increase in repeat customers!
heh!