I think it is unfair for you to say that the OP’s wife is neglecting her husband by not having sex with him. We only get one side of the story here, and you have no idea what the full story is. Maybe he doesn’t treat her with love and respect, or maybe something has happened in her life that makes it difficult for her to be intimate with her husband. I’m not saying any of these things are true, but for a woman sex is so much deeper than just intercourse.
Men are connected to their emotions through sex, and women are connected to sex through their emotions. If she is not being emotionally supported and fulfilled in her marriage, she is not going to want to have sex with her husband.
Sexual intimacy is not about just doing it because your husband needs it (though I do agree that sometimes a woman may need to just love her husband enough to lay down her objections), it’s about connecting to your spouse on a physical and emotional level that you cannot normally reach. It’s about renewing your marriage covenant.
If there are underlying issues in their marriage, that could be the thing blocking her desire for sexual intimacy.
What I’m saying is, you shouldn’t be so quick to blame the wife for not having sex when you don’t know the whole story.