Because that's not what being goth is about which is good because it makes the author's metric one that isn't also a target. It's a somewhat well defined subculture that doesn't consider itself counterculture and so is more a fixed black obelisk than something positioned in opposition to the current state of the world.

So I think the author has a good idea, that The Goth Index is a good proxy for how well a community will tolerate other ideas outside the norm.