"On floatplanes it is not as important to be weighed because they usually are not filled with cargo, but they too have a weight limit. Commercial planes also have a weight limit and they will sometimes have to reduce fuel before take off."
Helicopters require far MORE weight BALANCE, than floatplanes and has nothing to do with cargo. And actually floatplanes take far more cargo than any helicopter. I've taken planes in Alaska that denied passengers in favor of cargo, this has happened to me, but I was already a confirmed passenger. I've also taken some cargo and mail runs out of Ketchikan which used to be very cheap, but are still available.