No, we do have speed limit signs just as you say. It's just that they're pretty standardised. You very rarely see a sign for anything other than 50kph, 80, or 100, apart from situations like roadworks or other temporary hazards.
Reading your comments, I guess what I was thinking of as confusing is better defined as the weirdness, to me, of a country so big that there is so much variation. Even the idea of having states is so different; the huge population and all the detailed administrative and government systems that it requires.
NZ has much the same land area as the UK or Japan, but our population is only 3 million. That loosely divides into 1 million in the city of Auckland, 1 million spread around the rest of the North Island, and 1 million in the larger South Island, which is mountainous and very sparsely populated.
It's amazing to think that just one big city in the US can contain several times our whole population, and all jammed into such a small area.

Brunnen-"I like variation, and weirdness too"G