Why do you stay married?

If you are involved in an affair, tell me why you stay married? I need to hear it badly today. Tell me all the reasons a man in his 50's will not leave his wife of 35 years. Not a bad marriage, just not a happy one. Wife caters to him but also manipulates and controls him emotionally. It's almost like he is brainwashed. He's told me all along he can't leave so help me believe it. I really believe he loves me but I know love isn't enough. I can't compete with a home, business, grown children and dearly loved grandchildren. So just be brutally honest and tell me. Some part of my mind holds on to the fantasy of being with him. It's jading my thoughts and making me more unhappy at home.