I've flown on little planes, 4-7 people types, and the first damn thing you do is get weighed before you board. I get that commercial flights are bigger and can handle more weight, but I bet they would save a lot of money if they enforced weight limits or charged by weight.

They do in Samoa

Fuel burn is directly proportional to the weight of the plane, so this is the logical solution. But nobody wants to lead the change even though people have gotten dramatically fatter over the last few decades.

I'm doing some basic calculations and how that chair isn't collapsing makes absolutely no sense whatsoever.