Yes. Old people. See, my grandmother can't marry the man who has literally transformed her life--and probably saved it--because she'd lose what my grandfather worked so hard to give her.
Because she loses his benefits if she remarries, and they need that money to live on. And she isn't the only one in that situation.
Grandma is one of those old-fashioned women, one of those who is happiest when she cares for the home and her man takes care of the outside world. And there's not a damned thing wrong with being that way.
So I think that ensuring retired people are able to retain all benefits if they remarry is a worthier goal than preventing two people from legally binding their lives.