A wife may buy life insurance on her own life, or she may purchase a life insurance policy to insure the life of her spouse.
If you are married, you have an Insurable Interest in your spouse. In order to buy life insurance on another person you need an insurable interest in that person.
A wife may rely on her spouse for financial support, or may suffer a financial loss should her spouse die. Therefore, she may purchase life insurance on your spouse.
Also, a wife may wish to buy a life insurance policy tp insure her own life, providing financial security for her family if she should die.
Learn more about life insurance for married couples.