Hi John.
I would tend to agree with what you are saying in general. But nearly all of the popular forms plugins (Gravity, Formidable, Ninja) have phone number fields that validate against US, international, and (I believe) even a custom definable pattern.
They all make it work. Something similar in ACF is all that we are looking for.
+1
It would be very helpful to have this!
Thanks so much for the prompt reply and fix Elliot!