Yeah, but when clothes pieces are mass-punched in huge machines, slight differences in pressure or texture or sharpness of the punch can lead to one layer being smaller/larger than the other. I've tried on pants where one leg was a different size than the other, even. I know what size I wear, but I'm still gonna try clothes on before I pay anything more than about $5 for 'em.

And hey, that saves me from being surprised by the button fly ;)