Why do lessons about rocks always begin with igneous rocks?

The reason that rock lessons begin with igneous rocks is because igneous rocks were the first to form directly from the earth's magma.

Recall that all existing rocks on Earth were formed for the first time with materials that were already in it, since no new matter is created on our planet.

This is the case of igneous rocks.

These types of rocks were formed thanks to the hot magma that existed on the planet, and that as it goes out towards the surface it cools. When this happens, the materials and minerals found in this rock are formed and thus create what we know igneous rock.

These can be formed on the surface of the earth (extrusive rocks) or below the surface (intrusive rocks).

The rock cycle begins with igneous rocks, since, for example, we would not be able to analyze sedimentary rocks (which are rocks that, through a long process, destroy and re-form other rocks) without first existing such rock.