Currently. You MUST have reader hardware to accept the digital driving licenses, and LE do not have this handheld scanners with this hardware (TSA barely has any hardware deployed).If you drive a vehicle on public roads in the USA, everyone in every state is still REQUIRED to carry the original drivers license card issued by the DMV. Digital driver’s license is not legal for driving.
Some states like Colorado still have their older bespoke digital licenses, and have regulation that they MUST be accepted, and have deployed bespoke solutions so that LE can do so (basically, you send your info to the terminal in their squad car)
Drive over the state line into Utah? You're gonna have a hard time without a plastic card. Want to get into a federal facility (or through TSA)? Colorado's system is useless.
Also, if your phone dies, it is going to slow things way down and you could even wind up getting taken into custody (or at least be told you can no longer operate the vehicle). The newer standard licenses Apple supports will supposedly do things like share limited credentials with LE readers over NFC even while the phone battery is dead.