Perverse government incentives.
If his wife needs nursing home care, they will basically be impoverished by the cost of her care until they are left with nothing and then Medicaid will kick in.
If he divorces her, she gets half of their assets the nursing home drains only her of money, Medicaid kicks in and he gets to keep his half. With the help of a lawyer he probably gets to keep more than half.
Another perverse incentive the government puts on the elderly is Social Security.
Married SS benefits are less than the benefits the same two wage earners would get if they were not married. So, it pays people approaching retirement to get a no-fault divorce and live together as husband and wife without the paper. The government has made marriage a losing proposition for older adults who have no intension of having kids and few religious qualms about sex outside of marriage.
No, they hate each other.