On a related note, students at the military academies are nominated by individual senators and congressmen. Upon graduation, Congress passes a law to commission the new officers. (from a recent answer on Politics.SE)

While that fact isn't new to me, reading that post I realized that I am wholly unfamiliar with the rationale for such a system.

Why is it that civilian politicians are given the power to nominate cadets to military academies? That seems wholly outside the purvue of legislature, or politicians in the first place.