Man can have sex with a woman without falling in love with her. On the other hand a woman cannot make love with a man without falling in love with him.
Marriage life is base on love and sexual relationship. Man knows that it is not right to have sex outside but if this can maintain the relationship with her wife may not be a bad thing to do. If a man force himself not to have sex outside but cannot fullfilled that need in his marriage eventually will result in divorce.