Grrr, third time's a charm?

Futwick, there are several flaws in your analysis. First, relative minor is quite important, because many songs flip their tonality between the major mode and the relative minor mode (or minor and relative major)--this involves no change of "scale" but a very real change in tonic, modulating by a minor third. The overlap in chord sets, albeit of different degrees relative to the effective tonic, lends to fluidly transitioning from one mode to the other. It's similar to temporarily shifting the tonic by a fourth or fifth (as happens in many chord progressions and melodic passages).

Of course, many other songs flip between major and minor mode while keeping the same tonic, effectively changing their "key signature" or basic scale pattern. So while the relative minor of C major is A minor, the (absolute) minor corresponding to C major is indeed C minor. Two separate relationships, both important.

There is also no requirement for V7 to be composed only of natural notes in the minor scale; Vm(7) is also common, and used to predominate. Note that VII becomes a very prevalent chord in minor mode--some minor mode songs use only two chords: I and VII. (So do many Dorian and Mixolydian songs.) This VII chord is rooted on the minor seventh--though it's a major triad, it frequently functions as a rootless V7 chord, but a minor V7 (Vm7). The importance of the VII chord in minor mode trumps the simple chromatic alteration often used to transform the natural Vm7 chord into a V7 chord, which does strengthen the pull of the V-I progression but isn't mandatory. Minor mode poses special challenges for harmony, meaning that it requires greater flexibility and astuteness on the part of accompanists. If you try to stick to Im, IVm, and V7, instead of considering other variants of these same degrees, you're likely going to hash it.

Melodically, the minor seventh still occurs more often than the major seventh (except in leading-tone sequences like tonic-seventh-tonic), and melodies using the "belly dance" pattern (minor 6th to major 7th) still sound somewhat "exotic"--the reason the 6th is usually raised in ascending melodic sequences. The blues scale uses a minor 7th, as even does a lot of major mode music in country and rock. To assert then that the 7th should be major in minor mode is decidedly odd, contrary to predominant usage not only in minor but in most major modes other than "straight" major.

As I said, in practice all three minor scale variants are used simultaneously, according to context. To be complete, the minor scale would have to include both minor and major 6ths and 7ths--but that would confuse things even more than the three scale patterns (which reflect both the standard melodic variations and the main chordal variations). An understanding of all three is useful, but as Will implies, if you have an intrinsic understanding of how stuff should sound, NO scales are necessary. Not a terribly useful argument, since it just brags about one's own ability and cuts off a means to convey what one has learned to others, particularly via notation. We haven't yet progressed to the point that we teach and learn by mental osmosis. A thimbleful of theory, properly expressed, can accelerate learning and understanding significantly.