If you look at what is the constraint on boarding time, the element that really squeezes it is the overhead bins. It's not people finding their seats."
Carry-on bag chaos: Airport, plane headache is airline moneymaker
https://apple.news/APU17ngj4QI66N5mtHsAOaw
I just read this article (sorry, the webpage has a paywall) and was wondering what the flight attendants would say if you brought a full-size carry-on bag that was see-through and had nothing in it but a candy bar.