>The C major scale is universally agreed to be the simplest, most basic scale
No, it's not. There is no such thing as a "simplest, most basic scale." That depends entirely on your arbitrary choice of notation and conventions.
No, it's not. There is no such thing as a "simplest, most basic scale." That depends entirely on your arbitrary choice of notation and conventions.
So it's legitimate to ask, if we're going to letter our notes based on the notes of one key, why not pick the key that sounds the most basic and fundamental? (The answer is that at one time folks heard music in a different way and Ionian didn't have the priority that it does now; see my other comment [1]). It also probably doesn't hurt that Aeolian (natural minor) is arguably the second most natural and "default" sounding mode, so it's not nearly as weird as if we decided to letter the notes off of Locrian or something.