Here's why:

* Continental crust is thicker and less dense than oceanic crust. It's made up of a variety of rocks, including granite, which is a common igneous rock formed from the slow cooling of magma deep beneath the surface.

* Oceanic crust is thinner and denser, primarily composed of basalt and gabbro. These rocks are formed from the faster cooling of magma erupted from mid-ocean ridges.

So, while you can find granite in some smaller, less common occurrences within the oceanic crust, it's much more prevalent in the continental crust.