system
Given the following post, respond as if you're commenting on Reddit:
human
CMV: Marriage is not "just a piece of paper"

A couple weeks back I was reading a post on a different sub, where a woman's boyfriend had a change of heart regarding marriage, something she 100% wanted for her relationship and she was looking for advice on how to proceed. Many, many people in the comments lambasted this girl for wanting to be married, said that it was "just a piece of paper", and one person claimed that if she left her boyfriend over this she "didn't really love him".

Marriage is absolutely not for everyone, and that is totally fine.  But it's definitely not "nothing" and significantly changes the circumstances of a relationship in legal, economic, and social ways. It's healthcare access, power of attorney, parental rights, etc. It's one of the biggest things couples can do to build wealth for themselves and any children. Not to mention the huge spiritual connotation if you are a religious person. Also I do  believe it's helpful for the government to able to distinguish between a casual relationship and a life partner who can make decisions in your steed.

I have no idea where this idea came from, and now it's getting to the point that people (mostly women) get shamed for even wanting to get married. I don't get it, and I'm genuinely looking for an alternative understanding about this. 

Note: I don't believe that marriage changes the "love" part of a relationship, that should stay the same. But love is like 1/5 of what makes a marriage to me.

Edit: this is obviously not applicable to areas where common law marriage is applicable. If you get the status  of marriage, then getting married is obviously not that important.
gpt
Often what is meant by ‘marriage is a piece of paper’ is that marriage is a legal or social process that doesn’t fundamentally alter the “seriousness” or the dynamics of the relationship.

It is possible to have a serious committed relationship without being married. It is possible to be married and have a terrible, insubstantial connection to each other. Marriage doesn’t influence this; it’s just a contract you enter into. 

All laws are on pieces of paper. Saying it’s just a piece of paper doesn’t mean it has no effect. But it specifies the kinds of effects that are possible; contractual ones. Legal, financial, social - like you point out.