I figured since I have now been on both sides of the fence. The one wondering why my wife didn't seem interested in me physically, and now I am the one just not interested at all in physical intimacy, that perhaps I could talk bout how it feels to be in each others position. Maybe this will help people in the same situation as to what might be going on in the other persons life. It's usually not because they don't love you, or that they find you unattractive, or don't care about your needs... Most often it is because something else is going on in their lives that may even not have anything to do with you, it could be hormones, kids, stress, depression, insecurities and the list goes on...
One thing I can say is don't ignore it, that just devalues what is going on and makes the other person feel even less important. Tell each other how you feel and what's going on in your life that is making physical intimacy difficult. Everything worthwhile in life requires work, a good sex life is no exception.