Here's why:

* Abundance: Basalt is found extensively on Earth's surface, especially in oceanic crust and volcanic regions.

* Formation: It forms from the cooling and solidification of mafic magma, which is rich in magnesium and iron. This type of magma is relatively common, especially in areas where tectonic plates diverge or converge.

* Global Occurrence: Basalt is found on every continent and in the vast majority of oceanic regions.

While other mafic rocks like gabbro exist, basalt is far more abundant due to its origin in volcanic processes that are prevalent on Earth.