I recently had a young lady call for legal advice and she had been cohabiting with the father of her child. I asked why she had not formally married and she told me that the marriage license was "just a piece of paper" and she did not believe that it was necessary. In her circumstances, it may not have been needed. But:
I had a question by the daughter of parents that never married. They had lived happily together for decades, until the father passed away when both parents were in their late sixties. The question was: Can my Mom get social security as the unmarried widow of my Dad? Had they been married, she would have received at least half of the father's benefits as a surviving spouse. But she was not a "spouse" and was left with nothing. So perhaps not getting "that piece of paper" was not such a good idea.
Today I was told of a lady who lived with the father of her child for over 10 years. She gave up a lucrative job to take care of their child and to help the father get his professional degree and set up his successful professional practice. Now he is leaving her and she wanted to know what her rights are. If she had been married she would have been able to seek some form of alimony and some share of the wealth he had accumulated over the last 10+ years. But because they chose not to marry, she will be entitled to child support. Nothing else. So perhaps not getting "that piece of paper" was not such a good idea.
Under the law, this is not a moral or religious issue, there are very real economic reasons why there is a body of law to protect the rights of people who choose to merge their economic lives and raise a family. Every person needs to make their ow decision about how they want to live, but a marriage license is not "just a piece of paper." It has a very real legal and practical meaning.