Yesterday, some friends and I were discussing Kandinsky and the meaning he applied to the phrase "art for art's sake." He and I had used these words in discussing art that was purely decorative. An experienced painter of abstracts interjected that she'd always understood quite the opposite, that it was art that went to the edge..."to explore the guts of art...out(side) of the box" so to speak.
I'm not sure what Kandinsky would have said, but I think it can be both. It can be purely decorative, or it can be purely esoteric, dealing only with art theory and techniques. Let me put it this way, using handicrafts as an illustration. On the one hand, we have an old embroidered alphabet sampler--pretty, but with no message other than a display of needlework technique. Or, on the other hand, a macramé wall hanging, perhaps beautifully knotted with all kinds of interesting materials, textures, and colours, but likewise having little meaning to anyone but perhaps the artist. This is "art (in this case craft) for art's sake."
Now, getting back to painting, in between these two extremes, you find narrative art, religious art, conceptual art, "message" art, portraits, vanitas still-lifes, and other types. Other media, such as photography, may in fact, be primarily this type of art. But in any case, each genre is an example of using art for some purpose that may or may not be pretty; or strong in abstract formal qualities; but at the same time challenges the viewer to consider himself/herself, life, what it's about, what it's not about, hopefully making them in some small way a better, smarter, more broad-minded person. That's art for other sakes.
I'm not necessarily saying that this type of art, or "art for art's sake" are either one somehow better than the other or more noble; they're just basically different. I might go so far to say that "art for art's sake" could be likened to art for artists while the other is art for everyone else, but I don't think that implies a value judgement, just a difference of purposes and sometimes sophistication. "Art for art's sake" is basic theoretic research, which is of course, important in any field. But after that (and as a result of it), comes art for human consumption. The irony in this reasoning is, of course, that such art, regardless of style or media, moves back into the "art for art's sake" category once it begins to lack much social impact and thus becomes purely decorative. That is, it exists only for its own, intrinsic value.