Weighing passengers before a flight is to ensure a couple of things, 1; the weight of the passengers does not exceed the all up weight of the aircraft for safe flying,
2; balance of the aircraft, the pilot needs to know where the CofG is, the centre of gravity, if all the fatties were sat in the rear of the plane, his controls could be out of balance and he may not be able to trim the aircraft during flight. Worse case scenario, aircraft drags its tail into the air and the sinks back into the ground.
One one flight I flew, with 3 mates I had to refuse to carry some of their cases. Golf gear had to be paired back. I had forgotten until arrival at the airfield that, though there were 4 seats and space for luggage, because I couldnt get the turbo charged model I normally flew the aircraft I got was not capable of carrying everyone and their kitchen sinks.
2; balance of the aircraft, the pilot needs to know where the CofG is, the centre of gravity, if all the fatties were sat in the rear of the plane, his controls could be out of balance and he may not be able to trim the aircraft during flight. Worse case scenario, aircraft drags its tail into the air and the sinks back into the ground.
One one flight I flew, with 3 mates I had to refuse to carry some of their cases. Golf gear had to be paired back. I had forgotten until arrival at the airfield that, though there were 4 seats and space for luggage, because I couldnt get the turbo charged model I normally flew the aircraft I got was not capable of carrying everyone and their kitchen sinks.