for several reasons, one is a surprise that I should be able to reveal in a little while....*g*

Another reason why it's an excellent question is this: I have mostly bought prints that are on individual sheets. Such sheets can be standalone, but sometimes one design would spread on two or three sheets (they are called dyptichs and tryptichs). But woodblock prints originally were pictures featured inside books. It's because those illustrations were so popular that some artists begun to print them individually and sell them on their own, all the while continuing to create book illustrations. You can quite easily find woodblock print books for sell now, dating back to the 17th to early 20th century