So marriage is like 4000 years old BUT the purpose is probably LESS about "love and happiness" which is pretty new to the marriage, along with diamond engagement rings, that really only go back about 100 years...
But marriage seems that is was created/designed so that the man could have "true" heirs to his shit and not bastards. But I don't know if that word would have been around 4000 years ago but still the same idea.
Clearly today the idea, in America anyway, of a "true heir" is very different.
If you are married and happy, ask yourself this, would you be JUST as happy if you were not married but still living with the person and everything else was exactly the same, just, no piece of paper no sacrament. If the answer is yes, then for you, marriage is not a big deal.
Marriage wasn't recognized in the USA until 1913. Marriage gave a resembalance of order to this country, along with the reasons of heirs, etc that others mention. I believe a societal change took place when it was not considered taboo for people to just live together, as many do now. I'm sure some are just as happy and just as miserable as married couples, and in the event of a breakup there are less issues to deal with legally.
In MY world, organized religion played ZERO part in my decision to marry my wife, who was brought up and continues to be Catholic. I told her mom and dad that I refuse to marry my wife in a Catholic church because I do not condone the crimes many of those priests have committed against young people, and then are just transferred to a different location, only to continue doing the same old shit. (Disclaimer, I was abused by my grandfather from ages 5-8 so, in my world,
they would all be put to death).
I also did not want to be one of those strict Catholic/Greek/Jewish, etc parents that wanted my kids to grow up in certain religion and then not be able to marry the love of their life just because he/she was a devout religion that differed from my daughter/son. I had faith in my children to chose whom they wanted. And I would welcome them regardless of their religion or ethnicity. The only exception being a devout Muslim that follows the archaic Middle East philosophy.
I do believe in a higher power. I do not, and have never attended an organized religious church. I think they are phony. They're all 501c(3), and they do not answer to their parishoners, they answer to their boss, the corporation.
My son and daughter are both very religious, as are their children, all of whom attend church weekly. I've never had any problems with my children trying to push their religious beliefs on me, nor have I tried to sway them.
Lastly, and sorry for the potential TLDR. Marriage is awesome, IF the two people are of like mind. I would be nowhere near the man I am, nor nowhere as successful as I am without my wife of 47 years. She's my girl. We started going to shows, dances, etc when I was a young 16 and she was an old 13. Now I'm 69 and she's 66. It's been awesome, despite difficulty times as every person or married couple has experienced.
I knew my wife when she was in diapers, I grew up in the same neighborhood, am best friends with her entire family. Her dad put up grain bins for a living and her mom left school in the 2nd grade. And he raised 7 kids and they never went hungry. My mother-in-law was one of the most savvy people I've ever known, and I really loved her. She taught my wife, and all her sisters (she had 4) how to be a wife, mother and partner to their husbands. Not one divorce in that entire family. Her dad was Spanish and her mother was Mexican, born in Mexico. Didn't mean shit to me where they were from or what ethnicity they were. They were awesome people. I was honored to be asked to deliver a eulogy for each of them.
My mom was divorced 4 times, my older brother and younger sister were divorced 4 times. It's a killer, and sadly, some people just never learn. My mom once tried to tell me how to run my marriage, and I told her to keep her nose out of my marriage because her track record says failure.