An insight of Erich Fromm [in my words] from The Art Of Loving: People think that if a couple is physically satisfied then they will experience love. The opposite is true - If there is love then there will be physical satisfaction. What is clear is that if a marriage lacks physical satisfaction then it requires serious investigation to see what is wrong - because something is. The lack of physical satisfaction is not the primary CAUSE of the problems in the marriage [although it definitely exacerbates already existing problems] but an indication of deeper problems.
Another insight: Most marriages are just partnerships similar to business partnerships. Both sides have needs and seek satisfaction. The man satisfies the woman, the woman satisfies the man and they are both happy. There is one critical ingredient missing.
Just want to get people thinking. Elaboration is required.