The marriage contract is a way to regulate marriage without involving governing authorities but making it an internal affair between the spouses and their families. I want to make you free to choose, not have you locked into legal structures that may go against the Word of God. Therefore marriage contract is preferable over being governed by worldly laws that lack wisdom covering how to handle sad moments and events that unfortunately happen in marriage.
Marriage is a blessing of God over a couple, a man and a woman. God perfectly knows how to fit them so they can work together towards higher goals than just themselves. In order for a marriage to be successful, there are structures, how they should function, and who does what but without being constrained in the roles.
They are supposed to yield to each other with respect, but only with one in the leadership position. Only this way can a union survive no matter what media, ideology, philosophy, or what the world says. Therefore the husband is set as the leader over the wife lovingly ruling. Putting her before himself with a responsibility to protected and serve. However, she has to yield to his unselfish demands for working out their solution to the problems and obstacles they meet in life.