As far as I know, patrol cars (or roadside RBT cars) generally scan the number plate of every car on the road near them and alert the officer if someone’s license is expired/suspended/warrant for their arrest/etc.

Even before those existed, it was common practice to use a radio to ask someone back at the police station to run the number plate of a car they just pulled over. They want to know, before they walk up to your door and ask for your license, wether the owner of the car has a criminal record for example.

So - if they do ask for your drivers license, chances are they already know if it’s valid or not. They just want to see the photo and compare it to your face.