It is fascinating to me that most people assume (especially Christians) that the current definition of marriage has been consistent for thousands of years. In the post industrialized countries, we assume marriage has always been about two people providing emotional support for each other. However, this is quite a modern concept. Before the industrial revolution, marriage was about one person (usually the female) leaving her extended family to become part of another extended family (or tribe). Her emotional and physical support was from the broad network of women in that tribe, not necessarily her husband.
During the 19th century industrial revolution as men moved from their extended family to work in factories, their wife came with them. Both had now become isolated from the extended tribal family. Now, they depended on other for emotional support. Neither men nor women were prepared for this transition, leading to divorce, alcoholism, and spousal abuse. In the 20th century, we tried to repair this inadequacy by attempting to teach spouses on how to be that supportive partner as well as provide a civil support system in our system of laws. To some extent, it was successful. Yet, much work remains to be done as the divorce and abuse rate is still much too high.
An interesting and unexpected consequence had developed by the late 20th century and early 21st century. We had a large class of people who were same sex attracted who needed the emotional and physical support of the same sex, not primarily the opposite sex. This large group of people had been left behind without the emotional and supportive benefits of marriage. A need arose to provide the same civil and emotional support to those who are same sex attracted.
With marriage as defined today, it makes perfect sense to me that same sex marriage attracted couples should enjoy the same benefits and civil rights as opposite sex attracted couples. I am thankful the U.S. Supreme Court has now agreed.