Porn art is just art that happens to be sexually stimulating. Doesn't take away from the fact that it's art .o.

Anything created to stimulate an emotional response from the viewer is art. Erotic art is an extremely strong example of that.

It's because it has the (sex) and obvs the (sex) doesn't expressive anything but... (sex)

But yeah, good question. When it comes to art, there are terrific examples wherein artists utilize composition, colour theory, and display a solid understanding of form and structure. Certainly I might not consider a good lot of it tasteful, but that's the majority of it.

Maybe it's execution in intellectual or emotional evocation? Like, from the works of Da Vinci, to Van Gogh, to modernists (whose names I'm tragically unfamiliar with), their works are meant to evoke thought and discussion (as in examining the forms and techniques of older works), or they evoke deeper emotional responses (Van Gogh's 'Starry Night' is a wonderful example), whereas a vast majority of pornography is simple titillation and appeals to the more primal drives (be they vanilla or kinky). You don't look at a typical image of a dude bound to a bed, a chick with her breasts inflated to shit, or two individuals railing each other and become engaged with it more than what it does for your taste and/or kink. Hell, I'm guilty of such simple images when it comes to bondage. That said, unless it's doing a job of conveying a narrative or evoking an emotion (which many, many artists take the effort to do, mind) the typical pornographic artwork is about as well as Renaissance bowls of fruit at best and hieroglyphs at worst, and those are very much studied as art.

But, those are just my thoughts. Sorry that turned into such a friggin essay!

Because A: some artists can be snooty as all getout and B: They're probably trying to save face after getting turned on. XD