There is actually a deep unconscious thing going on with women when they want a man who is already taken. Deep in a woman's brain, she is on the lookout for a man who she KNOWS will make a good companion. This is set in a womans brain, she's born with it. If she sees a man who is already with a woman, she sees that man as definitely having what it takes to make a working relationship. Why? Because the proof is right there in front of her- he is with a woman. If that woman looks happy, there is an added bonus. If a man has a wedding ring on, to a woman's subconscious mind, that says that he has what it takes within him to maintain an ongoing, lasting relationship. Thus, an attraction to him turns on like a light bulb.