Because older divorcées have fewer options in the dating market.
Picture two married couples. Couple A got married at 21. Couple B got married at 31. Assume for the sake of simplicity that the spouses in each marriage are the same age, and neither one has had children.
At year three, Couple A stops having sex on a regular basis. Arguments become a daily feature. The wife begins pulling a beta valentine on her hubbie’s ass because she is turned off by his gradual betatization. They are now age 24, and divorce is whispered. Both of them survey their options should the unthinkable happen. Both realize, based on subconsciously acknowledged experience in the real world, that they could find new lovers in short order should the marriage fail. Divorce proceedings, while a testament to failure, don’t inspire them with fear and dread. There are green fields just past that horizon.
At year three, Couple B suffers the same fate as Couple A. The marriage has lost its allure. But this time, the response to impending divorce is different. The now 34 year old wife has stopped receiving glances from men when she walks around town to do errands. She senses, though she will never admit it even to herself, that her salad days are over and being single would not be the fun adventure it was when she was 21. The husband also believes (wrongly) that he has fewer options, because his marriage has made him rusty and dependent upon regular female companionship. He has doubts in himself and can’t imagine life as a single man. Both dread the repercussions of divorce and what it means to be thrust into a cutthroat dating market for which they are ill-prepared. So instead of divorce, they grit their teeth and he retreats to porn and poker while she has an illicit affair with her boss.
So there you have it.
Options = instability.
This is the kind of psychological analysis that you just won’t glean from a dry social survey that is prone to false information, particularly from female respondents.