@Supercyborgninja has mentioned the next step that would make this more universally acceptable and more practical.
before i read his/her comment i was thinking the same thing.
it would make it so easy to prove identity this way, without handing over a phone or watch physically.
with "tap-to-prove-identity" there would be a way to even hide the actual identity related numbers or even name from people if at a bar or store, with the only detail you allow to be readable on the bar or store's terminal is age, for example.
TSA and police would be able to get all the numbers and name and address. but in other situations you could select what info to be passed. much like in share contact details you limit who gets to see your profile picture.
there is a practical difference between proving your identity (and no copy of the info is retained by the other party; they just look at the id and say, ok thank you, and they dont retain any copy of the info) and proving your identity and they take a copy of your license for their (permanent records).