Go up to any 50 people in any major city and asks them what the divorce laws in their state are. Maybe 2-3 people would have any idea. To think that these laws, which most people are ignorant to, are the primary motivators of any of our decisions is flawed thinking. Economic parity and opportunity for women, undoubtedly is. But it is unlikely that the state of the law is what causes people to get or not get divorces.
This kind of economic theory/cost-benefit analysis always assumes a level of knowledge that the ignorant masses just don't have. The information is just not as wide-spread as the researchers would like us to believe. People are motivated by stupid shit, not divorce laws.

You assume that people don't have a working understanding of what the law is with regard to divorce? Perhaps. I suspect you are not old enough to have been around prior to the passage of no fault laws when getting a divorce was quite difficult. I can assure you that while people may not have known the specifics of the laws, the fact that divorce was readily available (because of changes in the law) was very much on the minds of people in the late 60s-70s, women in particular.

Regardless, today people do have, from their own experiences, or from society at large, understandings as to the increase in the divorce rate, the fact that alimony is less and less common, and they have a general understanding that it's fairly easy to get a divorce if you want one. They don't need to know the specific legal mechanisms to know, as many of my female friends have told me, that with half of all marriages ending in divorce, a fall-back plan is a good idea.

People may not have a thorough understanding of the letter of the law, but they still know that divorce is there--they know their options, even if they don't know every little nook and cranny of the way towards fulfilling that option.