Here's why:

* Continental crust is thicker and less dense than oceanic crust. It is primarily composed of felsic rocks like granite, which are rich in silica, aluminum, potassium, and sodium.

* Oceanic crust is thinner and denser, mostly composed of mafic rocks like basalt and gabbro, which are richer in magnesium and iron.

So, while granite can be found in both layers, it is the dominant rock type in the continental crust.