To bring her self-esteem down. If a woman feels like her husband needs some other woman to satisfy him, she feels humiliated and sad, this in turn may cause depression and low self-esteem. If she feels like this he may think that she will cling to him, start acting jealous and loose confidence in herself. A good man would never put another woman before his wife. My advice is to separate from him and enjoy life because he is out to destroy you.
coz the wives will take every chance when the husbands are not around to flirt with other men !
Because they can get away with it, or she doesn't really care.