Well, gonzo largely represents such a big arena of the porn industry that I'm surprised it hasn't swallowed it whole. Credit to the producers, writers and directors in the industry who competitively put out stuff like "Pirates" that maintain a couples' interest in pornography.
But really, gonzo porn, to me, represents the Cirque de Solei of hardcore porn, in a can-you-top-this sort of way. In some ways, it's the appeal of primitive, story-less sex, in a similar vein to the no-frills stuff in the B-Movie Action thread- there are no pretensions. And in other situations, if you're fond of pornstars like I am, you see young faces making their way up through the business, kinda like professional sports- they always start with gonzo.
A lot of it has to do with boundaries as well- how far can you push it before I'm turned off? How rough must the sex be, how misogynist must the performers act, to turn me off? For instance, at one point, at what point in "Bad Boys 2" do you stop and realize, "I'm no longer enjoying this unpleasantness?" Do you avoid the "MeatHoles" series, or do you watch the opening moments of each video before shutting it off?
I do notice a lot of couples are into gonzo, though, which could provoke an entirely different conversation involving the emotional-sexual give and take of a sexual relationship. Most girls I've encountered watch it with their man because they know it turns their man on, and they love seeing their man pleased. So the man reacts to what's onscreen, and the woman reacts to the man. Odd chain of events to me.