What's the point?
A driving licence has only one purpose, to show that you are licenced to drive a vehicle. You need to show it to a car hire firm if you're renting a car, or to a police officer when requested. In the latter case you have 48 hours to produce the licence at a police station.
That's it. So why would it be 'handy' to have it on a phone if you're only going to show it to someone once in ten years?
A driving licence is NOT an ID document. Same with passports - their only purpose is to be shown at borders to allow you to enter a country.
When someone asks me for photo ID I say i don't drive and don't have a passport, and what are they going to do about it. This is the UK, ID is an alien concept. If I say who I am that should be sufficient for anyone, unless they know to the contrary.
10 Downing Street