The fact that women and men have far less distinctive and more complex roles now is another reason why marriage may be considered out of date. Perhaps marriage is held together more effectively when both partners are completely reliant on each other for something ... In the modern era, people are single for longer. Many women have successful careers and are financially independent before meeting a life partner and men have learnt how to take care of themselves domestically. Contemporary unions are therefore not based on the same level of need or dependency as they were in the past, which may make them easier to give up.
It's hard to fault the logic of this. If men and women stay single long enough, and are encouraged to become entirely independent, then there is no longer such a strong social basis for marriage. It would seem inevitable that you will have a higher divorce rate in these circumstances.
Perhaps some good marriage advice for young couples would be: make sure that both you and your spouse are incompetent at something normally undertaken by the opposite sex! Maintain your interdependence!