Originally Posted by
Haven't a clue
My mother was a Hostess on Rapides post WWII. Part of her job was to weigh the passengers and allocate seats for weight snd balance purposes. She reported no one complained. She stayed on the ground when the flight departed; no catering on Lancashire Airways, and if there was, no seat for the Hostess to serve it.
My very first air travel as a passenger they did just that (mid 1960's, DC-3). When I took helicopter tour in Hawaii several years ago they did that as well.
Checked baggage involves more than just the weight - there is considerable labor involved in handling (and if bag is overweight there is even more as the baggage handlers have to take special care to avoid potential injuries).
Besides, as others have noted, due to modern yield management, chances are the people sitting near you didn't pay the same for their ticket as you did.
I haven't heard it being done recently, but some airlines used to force people over a certain weight to buy two tickets since they couldn't fit into one seat.