They don't require it to sit cabin. They will allow you down to talk to the crew depending on where you're at. They are almost as bad as the TSA about telling you how things are done. In HOU they make sure you know you go down before everyone else. They want you to board first and find room for your bags too. In STL if you ask if you should preboard they get on your case letting you know you come last and then tell you how it's like that everywhere. Each gate agent tells you the previous one wasn't doing it right.