system
Given the following post, respond as if you're commenting on Reddit:
human
[ELI5] Why are some pages "intentionally left blank" in some books?
gpt
Look at a book from the top of the spine sometime - you will see that the paper is glued in bundles - 8 sheet/16 pages per bundle. 

It is very cheap to make books with these bundles, so almost all books are printed this way. This means that the final page count needs to be a multiple of 16. 

Some of this can be taken up with "other books by this author" and other content, but sometimes, the pages are just left blank.