I mean, why would a bank care about phone numbers outside of the country it serves? Do you expect a US bank to recognize the number systems of every single one of the 195 countries out there when 99.9% of their customers live in one? Do you expect a French one? An Ethiopian one? Banks are explicitly not global businesses, they are generally national at the largest. It's not like they lose a whole lot of business if they don't support it; it's an edge case at best.
And Google certainly knows you are currently in a new country, but you could be there temporarily visiting, on a temporary residence, or have moved. How would you expect Google to know that? You likely also have to accept new Terms based on the country you move to, and there are more than likely fraud policies in place specifically to prevent people abusing a system like that to get lower pricing. The required step is there as policy, not a technical necessity.