There are countries which don't have zip codes.

Turns out that when I'm in the US, I can't use my credit card to order takeaway food online, because they universally require zip code validation, and neither the postcode for my Swiss credit card (8047) or my UK credit card (IV548JS) (both codes modified to protect the guilty) pass the very simple minded zip code validation.

...and Ireland only had them at all since 2015.

I think his point is that there would be collisions with every other country so it could only concivably work with one countries zip codes.

Well, the country prefix solves the collision problem, after which it's just a data problem.

Thank you.