Why are the Northern Lights always mentioned over the Southern Lights?

The Northern Lights are mentioned because far more people have seen them that the Southern Lights - because, as you said, there's a far greater (populated) land mass in the North.

There's also a more subtle reason - it's a North-centric World. Most of the population live in the Northern Hemisphere - and in particular, most of the population who might be concerned or interested in such things so there is a general "northern-based" mindset.

As an example: what's wrong with this story:-

"Two astronauts were on a ten-year journey into deep space. One day one astronaut said to the other 'I wish I was back on Earth now that Summer has come'"

The answer is, of course, that if it's Summer in one hemisphere then it must be Winter in the other and that many people fail to appreciate that fact, particularly if they live North of the equator.

I didn't even know about the Southern Lights, people know more about the Northern Lights that's all. Also schools only teach about the Northern Lights in Geography, but they should teach about the Southern too. :D

You're probably right. I know most of the time the northern lights are mentioned here in the UK is to tell us when we can see them - obviously the southern lights aren't going to get a mention like that on UK TV.

That might be the reason. I always assumed that those of us in the Northern hemisphere talk of the aurora borealis as it's the nearest one to us, and those in the southern hemisphere talk of the aurora austrialis for the same reason.

look at a map. how many people live south of, say, 40 degrees south? and where are they with respect to the south geomagnetic pole? now you know why 99.9% of aurora australis pictures are taken by researchers in antarctica, and people in new zealand.

Yep that's exactly the reason.