Ever noticed that a lot of non-American book publishers print their book spines upside down?

Those of you who read books published by both American and foreign publishers may have noticed that many foreign book spines are upside down. No offense, but they ARE upside down. One would expect that when books are stacked on a table face up, their spines would be right side up. While they are not always upside down (note Angeli e Demoni is upright with respect to the book cover, and Loriano Macchiavelli’s Delitti di gente qualunque is correct, the other three (publishers from Mexico, Germany, and Italy) are all upside down. This is not particularly important,  I realize. I just thought it was an interesting convention. What’s with that?