The seats are assigned. People have been standing in line for 15 minutes now. Why on earth would anyone want to stand there, when they could just sit and wait until the line clears?
I understand wanting to get off a plane ASAP, but boarding? You just end up sitting on the plane, waiting for everyone else to get on.
Big issue for musicians. Many of us have instruments that are just small enough to be carry-ons but just large enough to be a bit unwieldy compared to other carry-ons, so nabbing primo carry-on storage is a must.