The acceptance of no sex has me baffled too. If I go more than a week with no sex I turn into a whiny, *****y, pain in the ass. I can't stand to be around myself, so I'm sure my wife would grow tired of it rather quickly. I can relieve that to some degree with masturbation, but in my mind that isn't how marriage is supposed to work. At its core a marriage is a sexual relationship, at least in my mind.
I think it happens because many men are afraid to talk about it and most certainly afraid to do anything about it. I truly believe that the men with no sex are weak. Not necessarily physically weak, but mentally and emotionally weak. Lacking confidence maybe? This comes from a combination of societal pressures and the stupid **** love makes us do and put up with. So you get a double whammy. The men aren't willing to stand up for themselves which in turn makes them less desirable and attractive to their spouse.
For women, I think it is a combination of not being turned on by that weak man and selfishness. Attraction and desire are in large part mental, so I believe a woman has the ability to allow herself to be turned on by their husband, if they really want to. This is one of many things I absolutely love about my wife. She genuinely cares about all of my needs, including intimacy and sex. I give her everything I've got in all aspects of our marriage and she does the same. Upon reflection there are times where I know she wasn't really all that interested in sex, but she allowed me the opportunity to get her turned on. The result is great sex even when she probably could have lived without it, but she knows it is important to me and to the marriage and she will be fully engaged in it, no "starfish sex". I see it as a very selfless act and those selfless acts are the foundation of a great marriage.