alt Hacker News> I wonder if there's some way one can take advantage of the special properties of A[n] paper.
Not as a consumer. As a paper producer, you take advantage of it by cutting large sheets of paper in half to produce smaller sheets. Since you never sell any sizes that aren't clean multiples of each other like this, you've minimized the amount of paper you waste. That's the "advantage".
This was once the standard way of making paper; I don't know if it still is.
As a consumer I used to use it all the time, though it matters a lot less these days. Two A4 pages at 50% zoom (A5) fit on one A4. You could cut your printing cost for drafts in half by doing that, back when we had to actually print to check the layout. Same went for posters etc, and since the aspect ratio was preserved it was really handy to preview at home on A4 sheet before taking it to the print shop.
I’m sure you can do that on other size systems, but ISO paper sizing gives you accurate scaling.
Same goes for photocopies, photocopiers can scale copies so two A4 sheets copy to one, if you don’t need the same size.