I could go on for hours on this topic, but I'll distill the essence of my comment.
This is a nation that has virtually no spirituality to speak of. Everything is about the here-and-now, the down-to-earth. Speak to a "Gen X/Y/Zer" of the need to see the "big picture" and they'll show you their 401k statements.
In short, aside from the need to "not be alone," there is no purpose for marriage. They aren't about to admit they might want kids (and if they seriously DID want children, they'd have them when nature intended that they have them: In their 20s).
Even if they DO have kids, they just turn them into miniature, spirit-deprived, consumer-driven versions of themselves.
There's no "there" there. I don't see why they don't just drop the pretext that marriage is what they want, and be content to go from one temporary relationship to another.
At least it'd be honest.
Maybe where you live. That's the opposite of my (Generation Y) experience as everyone else I know is well on their way down that road (except for me, of course :P).