I agree in theory, but doing so would have been very difficult practically. The IPv4 header structure is very rigid, and it wouldn't have been possible to just add more bits to the src/dst fields without breaking things. The only reasonable route I've seen would have been to add an "area code" or "country code" to the Options fields and have huge border routers to translate packets between different locales. It would have solved one problem, only by creating an arguably much worse one.

https://en.wikipedia.org/wiki/IPv4#Header https://en.wikipedia.org/wiki/Internet_Protocol_Options https://en.wikipedia.org/wiki/IPv4#/media/File:IPv4_Packet-e...

It was not possible to make a "superset" of IPv4, if only because one of the early major blockers was that BSD Sockets suck by leaking low-level details of addressing so you'd have exactly the same argument of "why should I bother writing entire second copy of connection code in my application" for any superset you want to imagine.

Similarly, we have 30 years of experience that vendors will happily break optional headers or flags.