Question

Why do you need to assign oxidation states?

Answer 1

Oxidation states provide information on the tendency of an atom to react with another atom.

Explanation:

Oxidation states are one of the key descriptors of chemical information. It is the arrangement of electrons in an atom that determines its chemical properties, including how likely it is to react with something else.

Without knowing an atom's oxidation state we could not predict or control its interactions with other materials.