Cool things with wheels since 2006
It's not about the total hauling capacity of the air plane. To counter weight, you need more lift. To get more lift, you either need more drag, which takes power to overcome, or speed, which results in more drag which takes power to overcome. More weight for a conventional air craft means more fuel burned with all other things equal. Of course, luggage handlers don't appreciate the extra weight either. That's the advantage blimps have. Their cargo weight does not directly affect fuel efficiency.
Yes, and you didn't mention that the shuttle adds lift with it's wings, counteracting it's weight, and luggage can't do that. But, I did't point out the physics of the issue, just the face value funny perspective. We all need some more amusement, not a high school physics lecture