Same-sex couples who can't marry aside (they deserve protection), I don't see legislation like this coming to the US anytime soon, nor should it. However, it does stir up age-old questions about cohabitation. Janet Street Porter writes in the Daily Mail, "Cohabiting is a status that favors men — that’s why so many of them refuse to marry and women comply in order to remain with the person they love."
"In the majority of cases, moving in together doesn’t achieve permanence. And yet most emerging adults will cohabit. . . But like so many aspects of contemporary relationships, cohabitation is easier on men, and its popularity is a reflection of their strength in the sexual marketplace. Cohabitation is a win-win situation for men: more stable access to sex, without the expectations or commitments of marital responsibilities."
We all know couples who cohabit and go on to have successful marriages, and both Porter and Regnerus acknowledge it, but the important distinction both Porter and Regnerus make is bird's-eye view vs. street view (think statistics vs. anecdotal evidence): more cohabitations end than marriages. That's a quantifiable fact.
Blame it on men, blame it on women, or call it a draw — I don't care — but cohabitation is a less serious agreement than marriage. It's like saying "I'm here as long as it makes me happy," where marriage (ideally) says "we're here to make each other happy." We can all name couples, married and unmarried, who defy this stereotype, because every relationship is a little selfish and a little selfless. Only the two people in it can decide if they've struck the right balance. But whether they have or haven't, if cohabitating straight couples want the legal benefits of marriage, then they should just get married.