Here's why:

* Formation: Sedimentary rocks are formed from the accumulation and cementation of sediments, which are fragments of other rocks, minerals, or organic matter. These sediments are weathered and eroded from existing rocks, transported by wind, water, or ice, and deposited in layers.

* Surface Coverage: While igneous and metamorphic rocks are present, they are more often found beneath the surface. Sedimentary rocks are exposed because they form through processes that occur at or near the Earth's surface.

* Examples: Common sedimentary rocks include sandstone, limestone, shale, and coal.

Igneous rocks are also significant, but they are more prevalent beneath the Earth's surface. They are formed from the cooling and solidification of magma or lava.

Metamorphic rocks are formed when existing rocks are transformed by heat, pressure, or chemical reactions. These rocks are often found in areas where tectonic activity is high, but they are less abundant at the surface compared to sedimentary rocks.