Monogamy is important to most people because a partnership provides social, emotional and financial stability. Monogamy increases the chances of successfully raising children. It also fulfills the need for physical intimacy while decreasing the risk of disease.
Sexual relationships often result in children. Since the chances of successfully raising children are enhanced when two parents participate in child rearing, monogamy provides both partners greater assurance that the relationship will last and that resources aren't being squandered on other partners or children.
In addition to the advantages of monogamy while raising children, monogamy makes sense from a health perspective. Non-monogamous partners risk infection with sexually transmitted diseases, such as chlamydia, genital herpes, hepatitis C or HIV, which can then be transmitted to their primary partner. Some STDs are linked to infertility; others can be fatal. When both partners in a relationship are monogamous, the chance of either partner contracting an STD is minimal.
In the 2011 book, "Premarital Sex in America," authors Mark Regnerus and Jeremy Uecker found a strong correlation between monogamy and happiness, especially among women. During the bonding process, the brain releases the hormone oxytocin, causing feelings of attachment. Women have naturally higher levels of oxytocin in the brain, which may account for women reporting higher levels happiness.