Counterpoint: it's also worth considering the costs of breaking with tradition.
I mean, sure, nobody has to get married. But then you might not get custody rights over your children. It might be more difficult to pick your kids up from school. Perhaps it will complicate inheritance. You won't get the tax breaks. You'll have to explain your relationship every time you're introduced to more traditional people, which might include family, or various other people with whom you'd just rather not get into an extended conversation about your life choices. It might complicate banking, especially in case one partner is survived by the other.
There's a direct analog to this in tech. Sure, you're only going to win by innovating. But you have to do so sparingly, knowing that innovation is risky, expensive, and difficult. Sometimes, perhaps most of the time, it's best to "just use postgres".
There are certain things worth innovating on. Perhaps the exchange of some token item (a diamond) is worth one of them. For me, it wasn't, I just bought the stupid thing, and got on with my life. It's nice, it'll last, and it's a time-honored tradition I'll never have to get into 1000 annoying discussions over. Life is just too short, everybody knows it's a diamond, we're married, great.