This is an interesting question.
I think the concept of marriage has radically changed. So many of us are children of divorce, so we have little faith that 'just being married' is the be-all, end-all. I'm sure there were just as many commitment-phobes in previous years, only people are more open about being in long-term relationships without wanting marriage. We witnessed icky, sticky divorces and would rather have easier exit routes, maybe? We've been previously married and have unpleasant associations with both the concept of the relationship as well as the work of the divorce.
And some people feel, I'm sure, that government sanction does not make their relationship any more meaningful. Some believe in staying in relationships until it doesn't work for one or the other party, and an easy exit plan facilitates that sort of coupling.
I think the 'meaning' of marriage has changed because it has been politicized so much in the last several years, openly being offered to some, while being denied to others. I think a lot of younger people are seeing some hypocrisy in this. And for some relationships, it's the same old thing: one person stays with the other without the marriage contract, even though they might want it, for the sake of not delivering an ultimatum and being left alone.
Years ago (6 of them, at least) I had a handfast ceremony with the most wonderful man in the world. The love of my life. We'd both been previously married and had seen that the Piece of Paper did not make it so for our partners. Handcrafting a loving ceremony was what felt comfortable for us. We'd had 2.5+ years together, and this was the right commitment for us at that time.
We also feel very strongly that EVERYONE who wants to marry should be able to marry. So for years, we did not marry, in solidarity for our friends and loved ones who also could not marry. Thus, I could not get medical insurance through my partner's employer, and three years later, we paid for the birth of our son out of pocket.
We ended up marrying nearly two years after my son's birth, due to my need for medical insurance. (I'd had some serious medical issues at the time.) I love, adore, and admire my husband. Nonetheless, I think we both feel guilty that we have rights other hardworking, contributing citizens of US society do not.
What does marriage mean for me? It's the same commitment that we vowed to at our handfast: to be true to each other, to be each other's equal priority, to respect and value each other as partners and loved ones and individuals, through all that life throws at us. And to behave like mature persons in an emotionally mature relationship.
Our commitment was with us long before, and this is just the kind of people my husband and I are. We knew we were partners at the beginning. We were solid,and that feeling has only increased. Nothing could change that. Nothing but death can. Our relationship only deepened with our pregnancy and the birth of our son. We are still hoping for a day when there is marriage equality, and I am proud to call my partner "My husband", and my husband, "My partner". We are partners forever.
H.