I think it's pretty understandable if you're just going by serving size. The amount of sugar needed to make a lot of frozen items taste even remotely ok creates some pretty absurdly small serving sizes. And the fact that cans of soup or other combinations of difficult to sort mixes of solids and liquids have more than one serving seems absurd to me. If I was coming from a culture totally removed from this one and landing without any preparation I know I'd always assume it was a one to one relationship. That said, it's not the case for 99.9999% of people. Who are literally too lazy to flip the side of something over and look. I suspect it's a case of intentionally blinding themselves to something they don't want to know.