Not the paper, the stuff on the paper scales the same. Want a large poster and then also handbills to give out? They're identical. Got 15 full size sheets of colour information but now want to turn it into a pocket handout ? No problem, it's the same thing but smaller.

This feels obvious - of course it works like that, until your paper sizes aren't using this ratio (which the US ones don't) and then the frustration is apparent.