American illustrator Harvey Dunn had this to say about the philosophy that true art should be divorced from any moral, practical, commercial, or didactic purpose.
“We still hear some talk of ‘art for art’s sake.” The expression is about as sensible as ‘beefsteak for beefsteak’s sake.’ The artist who falls back upon any such refuge in explanation of poor work might just as well be shown the door.”
The term 'art for art's sake' is often attributed to Théophile Gautier. In its Latin form "Ars Gratia Artis," the saying appears as the motto in the banner around Metro Goldwyn Mayer's roaring lion.
Samuel Goldwyn is often alleged to have said to screenwriters trying to convey moral ideas, "If you have a message, call Western Union." Many movies don't have much of a moral purpose, but the big ones certainly have a commercial one.
While I'm on the subject of the MGM lion, here's a photo of how they filmed it.
The notion of 'art for art's sake' doesn't make much sense to me. Art has many levels of purpose, whether to to sell soap, to decorate a home, or to articulate shared dreams. There's really no category of purpose that's intrinsically more elevated than another. Great artistic achievements have sprouted up, fertilized by the most unlikely of purposes—such as writing music to help someone with their sleepless nights.
Most art has the sake of the viewer or listener in mind. So in that sense it's not done for its own sake at all. Even if a work of art were to be painted in chalk on the sidewalk of a dead end street to be erased by rain—it would presumably be made for the sake of the mental well-being of the creator.
I know what Dunn means—lazy students have used the line "art for art's sake" to justify poor work. I agree that great paintings are usually more than the sum of their brushstrokes. However, art is different from beefsteak. It can feed us on so many levels, from the eye candy of gorgeous shapes, to the indulgence of violent or bawdy entertainment, to the expression of the loftiest ideals.
Wikipedia on Art for Art's Sake