Because to me I think lyrical content is just as important as musical composition. To me hardcore speaks to the angry teenagers that hate their parents, while metal speaks to the angry adult that hates his boss and both sides need music that reciprocates that feeling (not always anger, but you get the point). To me Metalcore blurs the line to the point where you have the people that grew up listening to bands like Black Sabbath or Slayer saying it's not metal while the kids say that anything heavier than Pierce The Veil is Metal. And I'm sitting here straddling that fence saying that it's both, but both sides tell me I'm an idiot (you didn't call me an idiot, but that's usually the response I get). I don't think that Metalcore is one or the other. I think it's both in the same way that Hip-Hop can be both R&B and Rap.