Royal Mail / Couriers charge according to weight and size because that is what it costs to transport. This seems a fair enough idea, no point continuing to be polite about size on airlines when so many people are huge now, it costs more to move more. The alternative would be to charge everyone more on the assumption of a higher average weight, but higher fares for all would put off a lot more people.
Used to use the helicopter out to the Isles of Scilly quite a bit for work, if you only just fitted through half of the double door entrance they would weigh you with your luggage so that they could adjust their fuelling so that the chopper would make it there and back. This was great flying with the boss, I wouldn’t get weighed with my bag of hardware and a sledge hammer, yet he and his umbrella would every time, guess this reassured his fear of flying that they were putting in enough extra fuel to account for him.
