I just about never check a bag aside from a one off about a month ago. Once I was at the front of the line I went directly to a kiosk that displayed the ready splash screen without being called. You're right that people do not proceed and my take is that they do this simply because they don't know any better and not because they aren't supposed to. I was also a bit irritated as my flight was scheduled at 6:00p, delayed to 6:40p (thankfully, as I was running late myself) and people were moving so slowly that I was in danger of missing the new time despite the line only being about 10 to 15 people deep.