Why is the 16-page signature most popular and cheapest?

Question:

Why is the 16-page signature most popular and cheapest?

Best Answer - Chosen by Asker: You know, I never gave this serious thought before, even though I used to be a book production editor. I bet it has something to do with the weight of the paper versus the standard paper sizes that printing presses are designed to use. I wonder if it also has something to do with the number of folds that can be completed neatly on a piece of paper. A child's trick I once heard was that there was a maximum number of folds a paper could be folded into. Maybe 3 is enough to keep page size appropriate and not wreck the paper.

Overall it is probably a throwback to whatever was easiest when signature binding was first economically available. Publishing is notoriously slow to change its processes :)

Any other thoughts?