One such factor is the concrete expectation of custody-advantage in divorce.
Another is a complete lack of a morality system in the makeup of the marriage partners.
In fact, I think our present dating and premarital sex model is to blame. Cultures that practice some type of courtship (no shopping for a wife until ready to commit to marriage), have lower divorce rates. We certainly did until the advent of the car and the social dating scene. Sounds terribly old-fashioned, but it's true.