Divorce brings many complexities to your life. No, perhaps more accurately, it brings different complexities to your life. Take, for instance, divorce for a couple who is in their 50s or 60s. Their children are now adults, possibly with children of their own. So during the divorce, there will be no prolonged or contentious discussions of child custody or visitation issues, nor will there be any questions relating to child support payments.
When a married couple looks towards retirement, they hope to have achieved some degree of financial stability. With the children gone, they may sell the family home, and with the proceeds of that sale, buy something smaller and that they will own outright. This allows them to eliminate the mortgage payment and the hidden cost of interest payments on that mortgage.
Marriage is often said to be a journey. With many things, practice makes perfect, so you might expect with couples who have been married 15-, 20- or 30-years, that they would be unlikely to divorce after that amount of time, as they would have figured out how to maintain their relationship and their marriage.