Glad you mentioned 'next of kin.' This is the important answer. If you're married, you can do all that important legal stuff- make medical decisions if your partner is unconscious or indisposed, get the death certificate if that happens and give it to all the people who will need it.
Say your partner is in a car accident and you go to the hospital. There's no marriage, no forms, no nothing to indicate you're at all related to this person. You're just some dude or lady, showing up at some dude or lady's bedside. You can't make the decisions for this person. Even if, say, they have a horrible narcissistic mother they're estranged from- that mother, just by being the mother, can get all the authority to make decisions your unconscious partner would hate!
(Drawing from my own life. Fuck my mother.)
You can't even call the hospital and get information on them. If they aren't awake to indicate a release of information, the hospital can't let you see them, can't tell you anything.
This is just the first example that came to mind. The purpose of marriage is, it's a legal way to indicate that you're the most important person in the life of the person you marry. (And yes, depending on where you are and laws in your state or country or whatever, domestic partnership and other stuff can grant that, too.)
This is so weird to me. Maybe it's about who you are, or who you run with, but when I saw that Discord was about to go that way, I messaged my Pathfinder group and every single person there immediately hit me back with, "so where to next?"
On the plus side, if anybody reading this ever has reason to think that they might need to go into a police station and remove someone being held there, apparently if you and a friend or two look sufficiently the part, you can just walk in, in plainclothes, and claim to be Homeland Security, and just... take a dude and leave.
Tell ya what. Make it as easy for me to pop off a pound as it is for someone else to take a hair dryer out of their luggage and I will happily pay for all the extra boobs I bring on board after I remove the weight everywhere else.
Oh no, I know it's my fault. You know I have a folksy, colloquial way of speaking, and I type like I speak.