* There isn't more *matter* in the southern hemisphere. The Milky Way galaxy is pretty evenly distributed across the sky.
* Our perspective matters. What we see in the sky depends on where we are on Earth. The southern hemisphere has a different view of the Milky Way than the northern hemisphere.
* The Milky Way's core is visible from the southern hemisphere. The core of our galaxy is incredibly dense with stars, making it appear brighter and more populated from the southern hemisphere.
So, while there isn't actually *more* stars, the southern hemisphere offers a more spectacular view of the Milky Way's core, giving the impression of more stars.
