I think it's the whole stigma that's attached to tattoos and piercings. They are generally associated with anarchic personalities. Like drugged binging rock stars, gang members, he'll raisers etc. I think now days people are a bit more receptive to them.
Its the audacity of it. To put a symbol of social non-conformity on the most public part of our bodies, our face, is the biggest way to make a statement. By having a piercing on the most public part of your body is essentially you screaming to the world your views. In other words, there is little nuance had when one wears such a ostentatious body modification.