LOL. Actually, it takes more fuel to carry heavier loads, so even if the crash was more of a center of gravity issue that the pilots couldn’t recover from, flying lighter loads is cheaper.
I think the airlines would face a lot of blowback if they requested that heftier passengers sit towards the front to help maintain the center of gravity in a safer realm and reduce the chance of a difficult to control situation.
Perhaps that’s why they impose fees for extra baggage. It reduces the total weight if people pack less. (Although it is probably just a way to increase revenue.) Just a thought…