"Email is the lowest common denominator - everyone has an email address"
Sorry but you are misguided. I know some very old folk who don't have email, never had and never will.
And I know plenty of young people who don't have one either. Their email address is their phone number. Ever since Facebook changed the sign up from requiring an email to just requiring a phone number, more and more young people just don't do email. Or quite a few who have forgotten the password years ago and never bothered to reset, or forgot the security questions they answered. They just live without email, I know it seems crazy but that is how it is.