In EU at least you can switch mobile operators and keep your number; also there is some bank account porting system (not sure if you keep your number). Same way

In EU at least you can switch mobile operators and keep your number; also there is some bank account porting system (not sure if you keep your number). Same way E-mail porting should be also required, so I can keep my gmail address. If mobile operators could forced give up "their owned" number prefixes, and create (pretty expensive) technical solution, then why email domain holders cannot be forced to do same?