I have no idea if this applies to you but... you got me to thinking.
For some guys dealing with someone else on an intimate level can be more trouble than it's worth. The W's expectations can be vague or she could be judgemental or demanding. He could be clueless, know that he's clueless and doesn't want to venture into an area where he may be embarassed by what he doesn't know. It's safer not to go there.
Some Ws use sex as a means to control. He may be afraid of losing control and so doesn't want to get used to sex so he won't miss it if she withdraws it.
Or his mind is simply occupied on other things or he may enjoy the simple little pleasure of teasing the W. It can be a good ego kick to be wanted.
There have been many times I'd wished I didn't have a libido just so I could tell my W to pound sand. I became completely addicted to her and her charms. Then the week we were married it dried up and she had the upper hand on everything. My sense of loyalty kept me there long enough, hoping things would improve, until we had kids. Then my loyalty was to the children.
I can see why some men could want to present a seamless front with no ways for the W to "get her claws into me." Stay cool, aloof and *safe*.
These are just possibilities and certainly may not apply to you. Men don't all think alike.