If I'm understanding correctly, you're saying that right now the network doesn't have an exhaustive table of IP addresses to physical locations. It has a cache, and a hierarchy, and the path to a location of the IP is fluid.
But a system where every device could be directly contacted/identified like a Sim card, would effectively require a complete table of "what network is device ABC at". A table that is updated every time the device changes network connections. It would be like trying to change domain name to point to a different IP address.
The problem is, updating a domain to point to a new IP takes hours or days not seconds, so doing that every time a phone changes WiFi is not practical.
Is that a good summary?
Thank you for such a long and detailed post! I indeed did not know about things beyond the SIM, and I didn't know about the extra details about the country codes either. That is extremely interesting to me.
With the phone spoofing though, does that mean two factor with a phone number is basically useless? If I had authentication based on a MAC address, it would take seconds to break it. But I think, and sure hope, that auth based on phone numbers is more secure.
I think your domain name answer -- that for the most part computers didnt need them -- is a very satisfying answer.