I can't believe the number of people that come into our store that "forgot" their wallets ! Want to write a check and have no ID! One recently, open carrying, had left his wallet/IDs at his shop. Others leave their wallets/money clips in the vehicle, which is running in the parking lot, then bring it in, 3 inches thick with hundreds of $ cash showing! Meantime other customers wanting to check out have to wait.
(rant over)
My 20 years in the military taught me that I had to have my ID any time I was outside my personal quarters. I keep my wallet thin so it's easy to carry and on me at all times. If I get stopped I don't want to have to make excuses. I want things to go as smooth as possible and not have to depend on the officer to be in a good mood.