This is fairly remedial cultural anthropology of the society we work in, but it should be entirely obvious as to why being married is helpful if you have childr

This is fairly remedial cultural anthropology of the society we work in, but it should be entirely obvious as to why being married is helpful if you have children, including the same last name (or at least an hyphenated add-on) A lot of people in society use these short cuts to make fast decisions in critical moments. For example, your child and partner was in a car crash, you arrive at the ER, and you want to see them. Can you? The real answer is "it depends on if the nurse/doctor/receptionist lets you", not what the law says. All you have on you is your ID, last name "Crew" and your partner has last name "Smith". Ah, who are you says the receptionist, I'm going to have to call security if you don't leave. Or consider immigration, border guards, or any other number of more fluid situations. People, generally speaking, respect a married relationship and hold it up at a more privileged level. This is what the marriage equality fight was about, since people usually don't respond well to the clarion call of "but we have a legally binding registered civil relationship in the state of California!". That doesn't roll off the tongue as your partner is literally dying in the ER and you can't see them.