GM, at least, charges $12 for license brackets as an option. Mine was ordered in a state that doesn't require it, so would have had to make sure that option was ordered. Even then, they ship in the trunk and the dealer has to install them.
Normally, they don't notice / don't care. My car isn't exactly "low profile" and draws more eyes (and ears), so I was a little more noticeable. Usually, they use it as an excuse to pull you over for drunk checks. Three out of my five stops were on holidays.
2012 Chevy Tahoe LTZ - HD tow package
2017 Rockwood 2703WS Emerald Edition