>Nearly all maps we're exposed to growing up have North at the top of the page.

Heh, you say that as if I didn't know! ;)

I'm sure you've noticed that in computer UIs, all the "3D" effects are based on the sun being at the top. Same with geography -- it's easier for me to visualize the terrain if the sun is at the top. That means South-up in the northern hemisphere, and North-up in the southern hemisphere.

Always fun to watch that West Wing clip.