when man was designing the computer monitor, he designed it as oval. Somewhat like the horizontal oval of the human face. Then woman walked by and asked, "Why does it have to be oval?"

Man thought to himself and couldn't answer the question. So he went to build the rectangular monitor and that silenced woman. But never did Man expect that centuries later, apes would question it.

but really, i'm not sure if it is possible to engineer a pixel that is of any other shape than square, and humans prefer wide-screen to "tall-screen" and thus the rectangular monitor.