Different people like their art to be viewed in different ways. Whether this can be considered a cop-out from the artist is a point that can be debated. And, just as artists have different tastes in what they produce and how they wish it to be viewed (not everyone strives for exact likenesses in portraits, and not everyone seeks out a deep and profound meaning with which their art can be connected) those that view them often have different tastes and expectations too. When you look at art schools (only speaking from personal experience with being part of a fairly strong art department, mind, so don't take my word as the gospel), the instructors will often base the grades they give their students on more than just one factor. Technique will play just as big a role as concept and methodology, but even here the various factors may have emphasis placed on one individual piece rather than the whole. It is really a decision left up to the artist and the viewer (or, in this case, the teacher). I know many artists that put far more work into the underlying concept and driving subject behind their art, whereas others I know emphasize execution and correct technique (composition, color theory, line quality, take your pick), and then still others will focus more on the process that led to their finished piece (this can be a bit interesting, basically paying more attention to the journey rather than the destination). In focusing on one you may easily fail in another, but how terrible a thing that is is, once again, left up to you as well as the viewer.
That isn't to say that there aren't set rules governing each of these areas (and there are MANY that hold sway over them all in some form or fashion), nor does this allow an artist to simply throw up their hands and say 'It's whatever they want to see!' That is more of a lazy cop-out than honest artistic merit. It is true, viewers bring their own prejudices, memories, and general personal baggage whenever a piece of art (keep in mind, I'm using this as a blanket term for art in whatever form it may take; it is simply easier for me to refer to one's audience as viewers rather than something else) but yet and still the art itself must stand on its own strength and on its own merits, not on what is brought forth by those who see it. I have talked to professors about this, and among the things they despise when reviewing the work of a student, it is the insistence that the subject matter of artwork be dictated by the viewer and ONLY the viewer.
So, in a nutshell, while this is all about whatever floats your boat, one must really keep in mind that boat needs something to float in. Regardless of the medium, art can be viewed either way, both ways, neither way, or even viewed/judged based on entirely different categories. Just keep in mind that those categories ARE THERE, and dismissal of them can easily leave you with something bland.