Standard weights and consequential problems. I remember an incident years ago, on a small turbo-prop, I think. It was carrying a group of pax who had been to a coin collectors fare. They were stout gentlemen and had light overnight bags in the hold plus carry-on. The a/c performance was sluggish. Later it turned out that the carry-on contained their coin collection and was way over the 5kgs or whatever the standard allowance was. Each pax was a few kgs over the standard; multiply the whole lot by 30 pax and the overweight could be felt in the trim and overall performance.
I think they got away with it, or was there a crash? Some will remember better.