I think you have a point. Music theory was written to describe what composers had done historically. When Mozart writes a piece he doesn’t write in a “scale” using just 7 tones. He’s as likely to use a natural 7 as a flat 7… just he’s as likely to use a flat 3 as a natural 3. When he uses natural 6 and 7 in minor he’s not “using melodic minor,” he’s making a cadence.

There are a lot of reasons to raise the 7th scale degree in minor and the Musicnotes staff has done a great job of explaining them. When you raise the 7th, then the line is smoother when you raise the 6th as well. You do this usually when you cadence and the line is stepping upward to 6-7-1… so you raise these tones when you step upward.. and there’s no need to raise them when stepping down. Composer do this all the time. Theory books do their best to explain all of this without going into the depths of tonality by creating this artificial “scale” wherein every time you go up you raise these scale degrees on the way up and lower them on the way down. It’s difficult to understand out of context. It’s not as if composers are like “I’m writing in melodic minor go up so natural 6 and 7 now!” … it’s more like “I’m writing in minor… oh, here comes a cadence, now I’ll raise these tones to make the cadence work.” Composers use chromatically altered tones all the time… they alter these particular tones often enough its been codified into a “scale.”

But yes, Curious, it doesn’t surprise that you’ve had a lot of musical training and not seen the melodic minor scale laid bare in classical music or understood exactly why it exists in theory books. I think you have a point. If you can teach musicians why certain scale degrees are sometimes altered in minor and major scales as well that’s what it’s really about. A “melodic minor scale” is just a pedagogical tool.