Ah, so it dovetails with the whole "children get a name reasonably fast" thing. I was interpreting that as "ever, in a natural lifespan". My bad, haha.

I suppose a counterexample to that might be cultures which do not use script in general. Then, obviously, there’s no Unicode characters for these non-existant glyphs.

True, but there's little risk of a name being entered into a form without some kind of transcription.