There are two situations: non-low-cost airlines only have luggage tags when checking luggage, and give you a small note to stick on your boarding pass. Low-cost airlines, in order to let passengers take only one piece of luggage, all the others have to be checked (baggage license plate), and your carry-on luggage will also give you a brand. If you have carry-on luggage and you don't have a luggage tag when you board the plane, they will be in trouble. They just want to make more money.