Those are great for reading PDFs or ebooks, or anything really. Instead of wasting half the screen and having to zoom out and make the text small to see more than a few lines like in widescreen mode.
It seems like just chance that our screens keep getting wider and wider to the point where you have to swivel your head rapidly from side to side to see it all. They used to be pretty close to square back in the days of TVs and CRT monitors. The trend could have been to make them taller instead.
