Oh, I've seen them before - those big format ones are used a lot in place of hardcovers. Like I live in Denmark and most of the new books are in hardcover size but paperback (I guess because they're easier to ship?), so maybe they have them in airports because they're easier for passengers to carry?

It's the opposite though, they're harder because they're so big! You only have so much you can bring with you as carry-on, and some airlines are really strict about how much extra you can bring alongside your carry on bag