It's not daft. It's done so that when new editions of a publication are made and extra information is added, the page numbers do not have to be reformatted. If you have loose-leaf versions, then it's easier to remove one out of date page and insert two new ones. This is why there are extra pages.
If the sheet was left totally blank, people would then query whether there had been a printing error.
There's usually method behind the madness.
Cheers
Whirls