I don't think it's as easily cut-and-dried as it is for you, Andy. Because you don't have a family of Uncle Vitos and their goombahs, and because you seem to be from a family with roots that have long since naturalized, of course the alternative makes absolutely no sense to you.
But things change when, say, you have a wife who natively spoke Portuguese before she learned English. Or grandparents and great-grandparents you remember speaking Lithuanian and making Lithuanian food and celebrating Lithuanian cultural traditions when you grow up.
Or maybe you have a job or school that takes you from the country where you were born to other countries.
I don't think it's as simple as you make it out to be, Andy. Nationality is a complex answer, much like race can be a complex answer.
That said, I won't ever disagree with you when I can only roll my eyes at a bunch of Hong Kong-based descendants from Han Chinese who spew expletives at a player called up on the Italy NT because "they're not Italian enough". But if you you think that sort of national requirement is lunacy for players, how can you be so hard-line adamant that NT fans be held at a much higher standard than exists for players?