Married people now in the minority

Married people are now in the minority in the U.S., at just under 50% of the population. The article notes that while people used to get married in order to have sex, now they get married to have children, but fewer are having children because of the expense. Living together is seen as a way of "test driving" marriage, ostensibly in view of the prevalence of divorce, but others have made the argument that those who live together before marriage are more likely to divorce compared to those who do not. (On the other hand, those who do not fornicate likely have a higher view of marriage in the first place, and likely have a strong aversion to divorce.)

I thought the woman who made the comment that she and her live-in boyfriend probably make more of an effort at the relationship because they don't have the "false security" of marriage to be rather cheeky. First of all, I'd like to hear why she thinks marriage provides "false security". It may be true that thinking your spouse will never, ever divorce you no matter what might lull some people into complacency, I think it's just as likely if not more so to spur you into making the relationship work, versus the cohabitation model where there is nothing preventing either from severing the relationship. I wonder also if she is thinking that the fear of getting dumped is a stronger motivator than wedding vows. That's really sad if that is the case.