I live in a country with the equivalent of a Real ID and a law requiring you to present it when asked. Officially they are supposed to have a good reason for it, but in practice they'll happily do it just because they can. And they'll continue "just asking questions" if they feel like it. You're not under arrest of course, but they are happy to waste a few hours of your time when you "refuse to cooperate".

After all, as a law-abiding citizen you don't have anything to hide, do you?