Given that many of the depicted countries list as having "sufficient production", I guess it's for the usual reason.

For those wondering what the usual reason is - https://www.reddit.com/r/MapsWithoutNZ/

That is just a subreddit, I don't really see where it describes the problem.

Anyway: It's because on the Mercator projection, it is a small point in the bottom right that easily gets overlooked or accidently cropped out.