It gives me a chance to get help in becoming the best person I can be from my life-long partner who is committed to helping me achieve that goal and allows me to help amy partner...presumably my life-long partner...become the best person she can be. And if by chance TOGETHER we have offpsring then as a team we can help our offspring to become the best people they can be.
It don't get no better than that.
What does marriage have to do with becoming the best person you can be?