It is difficult for anyone to understand how terrible it is to be in a marriage with someone who simply does not love you anymore. You see: to come home to nothing is a terrible pain.
Human beings need love and affection like plants need water. We are dry and half dead without it. We marry in order to make that love become part of our everyday life. But when that love departs, we are scarred because the very nature of love requires vulnerability. Love, as it where, opens us up. And the nature of rejection hurts us in that very place. No one can hurt you like the person that you love.
For some, it is easier to leave then to endure this unique kind of pain.