I think the main problem with some people today, as I've said before, is that they simply just want the easy way out to avoid hassle. Marriage requires even more than just commitment, it also requires the wedding itself: getting a license, getting rings, booking somewhere to have the wedding, booking somewhere to have the honeymoon, all that good stuff, so a lot of people today just adopt this mindset of, "We don't need a piece of paper and rings to prove we love each other", since all they clearly want to do is just get in bed with each other anyway... this is also why, unfortunately, some states have adopted what they call, "Common Law Marriage", where if couples, or, "Domestic partners" have lived together for X-amount of years (10 I think), by law, they can be recognized as being, "Married", even if they actually aren't.
I suppose it could be nice if love didn't have to require a lot of legal mumbo-jumbo, but the thing of it is, all that legal mumbo-jumbo is still important, like say if the woman is a dependent of the man, or is in need of life insurance? She won't see any benefits unless she's legally married to the man she's with. Or, as has been mentioned lately in the thread, there's the subject of the kids: what would the identity of the kids be if they were born out of wedlock?