I'm not a woman but, being married, I sincerely believe that most women (not all) find personal achievement in motherhood, which itself will thrive best within a lasting commitment, whether you call it marriage bond or anything else. The advantage of marriage is that it is a formal contract which provides a secure legal frame whereby each part knows what is involved, for parents as well as for children. Same reasoning when there are no children. Yes, marriage helps approaching happiness. One small detail though : it has to be a happy marriage, full circle.