I've never been in a relationship where I wasn't the one wanting it more than him. But I have a lot of male friends with the problem and what usually seems to be the issue is the word: "Perfect". When the women become mothers, they stop thinking about themselves and dedicate their lives completely to having a perfect child, a perfect home, a perfect blah blah blah... Everything needs to be picture perfect.<br />
Some of my friends have to make sure the dishes are done, the kids are sleeping, the clothes is in the dryer, the kitchen is clean, the flower's for mum's birthday is ordered etc. before she is able to sit down and then it takes hours of massaging her back to get her to unwind. It kills the mood completely. It's too much work to get just a little bit of attention. And even then they guys have to deal with the hurt of being the only one wanting it...<br />
The fact is that sex is like exercise. You need to have it to want it. The more you have it, the more you want it. But once you get out of shape, it takes a lot to remember how good you feel from having it.
I've been learning, in my own marriage, that my wife's seeming lack of interest in intimacy and sex is, to a significant degree, the result of her not expressing openly what she feels inwardly. She really desires intimacy much more than she expresses to me. So, if I rely on the verbal and non-verbal messages that she send to me... I will quickly conclude that she has about zero desire for sex. But there is always more to the story... Her internal desire for sex tends to rise and fall with the health of our relationship. So the more emotional energy I pour into our relationship... the more she desires sex. This leaves me in an interesting situation... for I need to engage in our marriage relationship in a totally unselfish manner for her to feel most interested and energized to give back to me intimately. That's not always easy for me to do... but when I work at it... she is always ready and waiting for me in bed... :>)
My second wife was that way. She was a very domineering person, and sex was on her terms, and her timing. After a couple of years of mediocre, infrequent sex, she totally lost any interest. "Infrequent" became every two or three years. That was a drastic change for me, after having been married to a nympho for 19 1/2 years.
I don't know, but I'm glad I don't have that problem like a lot of my friends...