I'm betting it's not just because it's a "false" image, but because it's a positive, happy image. Same reason critics celebrate John Lennon and sneer at Paul McCartney. It has to be bitter and maladapted to be true art in their eyes. Anything cheery and sunny is automatically dismissed.
On October 10, 1980, Mark David Chapman sold his beloved lithograph of Norman Rockwell’s Triple Self-Portrait to a Hawaiian public relations man for $7500. Chapman, who was strapped for cash, used the proceeds to quit his job, purchase a .38 revolver, buy airfare to New York and book a room at the Waldorf Astoria. From this base of operations he would stalk John Lennon at the Dakota and finally, in December, take his life.