Marriage is neither a mere financial contract or a mere declaration of love.
The one is a nice frippery introduced by the state to something far larger and more important than the state.
The other is nice (but not necessary) for the WEDDING, but for the marriage? No. It's part of the infantilized and unrealistic expectations people have of marriage that lead them to expect Romeo and Juliet from the thing, and start becoming discontented or assuming it has all gone wrong when the reality sets in, which is mostly hum drum and about getting on, fulfilling your role, avoiding resentment by not believing you are entitled to things all the time, and working to uphold the marriage.
In my experience, people with the special certificate from HMG lie to, beat, cheat on their spouse or steal from them in court, often hypocritically pretending to observe their religion, then spouting empty promises to God, empty because they do not believe in Him and blow tens of thousands of pounds on a party, before settling in for a life of resentment and emptiness. For me and many like me, the state marriage is meaningless - out of respect for the institution of marriage.
I think it's a bit rich to look down on other people's marriages because they just got on with the business of living and working on a marriage, raising children and so on for the rest of their lives, but didn't have an open bar at the local Rugby club.