It depends how you would define Marriage.
Under Religious, and Cultural, traditions, Marriage is a pact A Male and a Female make with God, to fulfill the sacredness of life, and multiply. That's it in a nutshell. (This comes from knowing my traditional wedding customs, and how presently, both the Native and Catholic marriage traditions are followed, within some tribes here in New Mexico, I think all of them do anyways.)
What it means now, is a legal contract between two people.
Also....Could be the effect of being "Young, dumb, and in love" and jumping into things without thinking about the consequences, which is how society is today.
So it could be a mixture of both Cultural/Religious Traditions not being followed by many people anymore (and that is something that is happening in every Culture, and Religions of the world), and Society jumping into things, with disregard and with no care for the consequences.
This ties into the having kids topic for me as well.