Sometimes that instinct serves us well, though. My understanding is that dented cans really can be dangerous: if the dent includes any level of break in the can

Sometimes that instinct serves us well, though. My understanding is that dented cans really can be dangerous: if the dent includes any level of break in the can's airtight seal (even something too small to see) then you're at risk for serious food poisoning. And even apart from illness, a badly dented box of (e.g.) corn flakes might well contain more than the usual amount of cereal crushed into dust. Rough handling can impact the quality of a lot of foods. So I don't want to cheer for waste, but I don't think it's fair to write off this heuristic as completely irrational, either.