Despite seeming incongruous, a page in a book without words is something we encounter so often we rarely stop to think about it. Pick up virtually any hardcover or paperback title and you’re bound to see at least one or two blank pages in the front, back, or both. Why?

According to layout artist Stephen Tiano, the appearance of wasting paper isn’t actually costing publishers money. “It has to do with signatures,” he says, which is industry talk for the groups of pages that printers fold and cut to assemble a book. A signature can be as few as four pages or as many as 32 or 64—all divisible by at least four. If the work is 200 pages, it could fit perfectly. If it’s 203 pages, that means there’s likely to be a page leftover from one of the signatures.

To offset the expense—one extra page of text could require an additional four-page signature, with three wasted sheets—designers like Tiano can try to condense the layout by playing with character spacing. Called kerning, reducing the room between two specific characters throughout a book can eventually add up to an entire saved page. “It’s not at the forefront of your mind, but if you have choices that allow you to land on it, you do it,” he says. “Otherwise, there’s waste.”

Not wanting to pay for paper that goes unused, some publishers opt to fill the extra space to feature checklists of an author’s other work, excerpts from other books, or illustrations. For instruction manuals, textbooks, and other niche publications, they might print the phrase “This page intentionally left blank” so the reader isn’t concerned they’re missing any vital information.

Blank pages are such a routine part of the reading experience that Tiano has gotten requests from some self-publishing authors to purposely insert them into their projects. “Some of them request one in the front and one in the back,” he says. “They think it’s just tradition.”