Mellencamp wrote the song himself, in response to how the music industry was attempting to hide his "real" image, which included adopting one of his previous stage names, Johnny Cougar.
"[1] Referring to his false image in his early years as a musician, Mellencamp was upset with the choices his manager made, including performing under the stage name "Johnny Cougar".
As a result, he avoided common practices that musicians undertake, including meet-and-greets and radio station concerts.
[1] Mellencamp wrote "Pop Singer" in the midst of a divorce with Victoria Granucci, at which point he began to analyze what he had become as a musician, referring to his image as a "monster" in an interview with Rolling Stone magazine.
'"[2] Cash Box called it "a strident declaration that Mellencamp is not a pop singer" and said that "he drives the point home with a mean-spirited guitar growling across the track.