Here's why:

* Igneous rocks are formed from the cooling and solidification of magma (molten rock) or lava. They make up the majority of the Earth's crust.

* Sedimentary rocks are formed from the accumulation of sediments, such as sand, mud, and organic matter. While they cover a large area of the Earth's surface, they represent a smaller portion of the overall crust compared to igneous rocks.

* Metamorphic rocks are formed when existing rocks are transformed by heat, pressure, or chemical reactions. They are less abundant than igneous rocks.

So, while the exact percentage varies depending on the region, igneous rocks make up a significantly larger portion of the Earth's crust than other rock types.