Gotta agree with the one that said it is a lot more than a legal or financial document. That feels like a characterization marriage received half by the raging of the gay marriage debate and half by this being the first generation experiencing the 50% divorce rate. Not that this should necessarily become a debate, but maybe to offer some perspective to people saying stuff like that and see if you still think it is just a financial or legal document.
One of my uncles was married for a great many years to his wife who was renowned in the mountainside as being a real c word unlike anything Godzilla or Feminism could hope to match. The sort of woman who gave rise to the Salem Witch trials. Now, I'll leave aside the fact he didn't divorce or kill her and hide the body early on, although I suspect that was driven by aspects of marriage not legal of financial as well. Around the time she and he were turning sixty she got diagnosed with (I may have this detail wrong) Alzheimer disease and was becoming even meaner than the ninth level of hell she was before. Now, no one, literally no one would have blamed him for plopping her in a home and running as fast as he could. She was headed for mean potato brain land fast and she wasn't really a saint. Instead, he took care of her until she died about 9ish years later with only slight help from her sister and during the end a in home nurse. And that isn't like taking care of a cat where you clean the litterbox and make sure there is food and a toilet to drink from. Think of an adult sized baby who hates and is frightened of you. His vow to love, honor, and protect her meant a lot more than financial or legal connection even though you could not have found a less deserving woman if you tried. It was partially religiously motivated certainly, but it was also that what he'd said when they were 20 still meant something forty years of unhappy marriage later. That's the sort of dignity and honor that comforts you on your death bed by knowing you meant what you said and you said what you meant.
And since someone already mentioned the religious, I'll mention the more...philosophical? (Probs bad word, but still).
I don't think anyone who gets married and stays married thinks it is going to be easy. Most know it won't be a peachy walk in the park. Stuff happens and life is hard. This isn't something I think is being ignored.
I think marriage for two people is as much a statement and promise about themselves as it is about the other person. It isn't just them saying "I think I've found someone I could tolerate hanging out with day in and day out until one of us croaks no matter what". They're saying "I promise to be the sort of person that no matter what happens I'm still here when things aren't fun anymore and may never be again". It's a hefty promise to make about yourself and about how you feel for another person. Dare I say an ambitious statement.
But that's what marriage is truly. It's making an ambitious promise and spending your life living up to it no matter how many times running away seemed like a good idea. And it might totally suck the entire time, but the point is that at the end if you kept that ambitious promise, you, like any other person who has done something terribly difficult and painful, can be proud of your achievement. And it is an achievement to take on that ambitious a promise and then succeed.
As for the piece of paper thing being put forth, committing to someone else financially, legally, medically, emotionally, physically, is a really hefty bet to make. That's called being all in and hitching your horses to the same apple cart. Now, call me judgemental, but that's more than a piece of paper and it's a lot more commitment than just being unpapered partners. Like, even the saying it is just thing smacks of calling grapes sour. If it were little, I don't think you'd have an even mildly strong opinion about getting one and you certainly wouldn't bother to degrade the concept.