Strip the songwriter away and the performer is just a person shouting in a room. Practical consequence: if we credited performers above writers, we'd be paying the microphone more than the person speaking into it. That's absurd. A singer can be replaced; the song endures. If the performer deserves top billing, then the guitar tech deserves more than the guitarist, since they both just service the instrument. Ultimately, the song is the product, the performance is the packaging. You can't sell the package without the goods inside, and no amount of charisma changes that.

Look, I get it—you're saying a performer's interpretation can make or break a song. But if that were true, then a karaoke singer who belts "Bohemian Rhapsody" deserves the same credit as Freddie Mercury, and every wedding band covering "Wonderwall" outranks the guy who wrote the original. That's obviously nuts. The performer just re-sells the emotion; the songwriter manufacturered it. If we credit the interpreter more, we'd also have to credit the translator above the novelist. The song exists on paper before anyone sings it, so the writer's hands are still the ones that built the thing.

The other side acts like a great singer somehow creates the song, but they're just decorating someone else's house. You can paint a wall gold, but you didn't build it. Without the writer, the performer literally has nothing to say. The voice is the weather; the song is the ground.