Some airline someday is going to figure out that if you guarantee overhead luggage space, people will pay more to get on the plane last instead of first.
But if you really want to pay more, and are flying on higher fares, getting on the plane first turns back into a perk cause you get some free booze. And your seat is now more comfortable than the airport seats (even many airport lounge seats, where the best seats can go quickly when it's busy).
