I have had exactly this conversation this very week with a young friend of mine whose live-in boyfriend says, "why does a piece of paper matter?"
It's a specious arguement and a dangerous cop-out any partner should heed.
My friend said, 'Okay then, if it's just a piece of paper, you won't mind if we have one to prove we're married, will you?'
A piece of paper matters when you graduate.
It matters when you pass your driving test
It matters when you're in hospital or crossing a border
Making a public statement of commitment, religious or secular matter to most people because it's psychologically important to do so.
Why do we give people flowers anf gifts at special times instead of just congratulating them or telling them we love them?
But I was judgemental (and see no harm in that) and advised Sienna to think very carefully about this person and whether he really is right for her. Fortunately, not in a position to buy property.