Without speaking for your wife, but speaking for myself and my parents, its NOT that we had any trouble wrapping our head around it, just that meat by itself didn't taste that good. Even in the US it is common to add other ingredients, like cheese, tomatoes, onions and tomato sauce and mustard to the burger. Otherwise you're just eating cheap meat and bread, and there's nothing noble about that IMO.

Even at fancier places which ground up better cuts of meat and bake their own bread, there are condiments added to the burger, both in the patty and after it is cooked.

That's the thing, in a burger with little else I find there is a taste in the "meatiness", partially that's a matter of texture and moisture, although there's some other qualities of meatiness which I am not qualified to elaborate on. I do like having some seasoning to the meat, at least a little salt, but with an underseasoned burger with decent quality meat and not overcooked, there's still something there that I appreciate, whereas my wife would find nothing redeemable.

My wife has the better tongue for many things, for example there are many vegetable dishes she likes which I find boring, I think the water-i-ness of certain vegetables bothers me more and she is able to look past it to see the other flavors. But I still find I am better able to appreciate that aspect of meatiness.