I think I've just figured it out.
Of course, I could have answered the question meerly by going into the visitor's center, but at the time it only seemed like a minor curiosity. Then it turned into an annoyance, and led to a certain amount of indignation, but by then I was far away from the visitor's center, in a different country even. So I continued to stew, until I found one of those 'well of course' answers.
In the National Cemetery featured in my last post, members of the military have their name, grade, dates and sometimes posts engraved on the headstone.
Then there are whole sections where the headstones have dates, but no names. This is not a place for the fallen whose remains could not be identified with certainty. They're marked "His Wife" or "His Daughter". I suppose there must be "Her Husband" as well, though I didn't see one.
It's not possible to know who's wife or daughter. There's no name on the stone at all, either his or hers. There's no grave nearby that the nameless woman is associated with. If you go there looking for your Aunt Mathilda, you just have to know where she is.
I thought it was awful, to be stripped of all identity like that. "His Wife". Not only does the woman not deserve a name, but not even her husband's name is there. Mrs Jones taken an appalling step too far. These names were not lost, they were deliberately deleted. Reduced in death to an appendage of an anonymous "Him".
But then it is a military cemetery. Women from the services have fully informed headstones. Spouses and offspring who were not members of the military, however, don't receive the same level of recognition as those who were. It makes perfect sense from that perspective. You might debate whether spouses and children have their place in the National Cemetery at all, and I guess this is the compromise. There are no family groupings, no names for non-servicepeople, but they're there within the gates.