We do have to show ID. But the federal government said it's not enough to use a normal state driver's license or passport. You need a special "Real ID" that's somehow allegedly better. Your old driver's license that you can pay for booze with, open a bank account with, and you know, drive with, isn't proof enough of who you are to ride on a plane.

Edit: I should note that I have one. But lots of people don't, because most people never replace their driver's license card.