You could have said the same about using a GSM provider's SIM card back in the day. Yet, now we can easily switch the provider without changing the number.
It used to be before government regulations were put in place. I don't care much about the technical feasibility currently. When and if a law is put in place it becomes up to the developers to create a solution.
Ownership isn’t a problem developers can solve, but lawyers will line up for it. After 50 or whatever years there is a lot of calcification around email.