What is it about NN that makes them popular in your country?
A person who used to be a regular here was of Greek ancestry, he said NN were very popular and well liked in Greece.
I've read bits here and there about NN in different countries and areas being held in high regard- some places in India, Africa, South America(many of theirs also lay blue eggs). A common thread was they did better than other breeds, including introduced "Western" breeds like rhode island reds etc.
Out here, they definitely are not "popular" but they are becoming better accepted than before. Sometimes when I sell my birds, the buyer will mention they had been looking for NN for a very long time and so they are extremely exited I have them for sale, some of them are just so excited they buy all of what I have for sale.
The more usual story though, is someone who came for something else- for me it usually was for peafowl, the person would have no interest in NN before seeing the birds- oh ewww they are so ugly! I do NOT want any! No no no!... and end up leaving with one or a few.
Another odd thing- it comes from all sorts of people, from friends of family or people coming for peacocks or other breeds of chickens just assuming really weird things about the NN... like they were feather picked by each other, they had mites, and in one case- someone thought I actually SHAVED their necks even though I'd shown him NN chicks not even a month old yet.