It's not clear to me that communication and use of email addresses works significantly better than communication and use of phone numbers.
Paradoxically, though, the UK then adopted alphanumeric postal codes while the US uses numeric codes.
In all of this, if you are claiming usability benefits, you need to say what your metrics are. Ability to recall numbers? Ability to dial numbers accurately? Ability to communicate numbers accurately, e.g. looking them up in a phone book? Efficiency or effectiveness? You also need to define the users you are targeting: the average, the old, the disabled?