Why do people think I'm emo (short question, if that's what you guys need)?

Ok, I wear black T-shirts and Vans basically every day, and I like skulls. I wear moderately tight navy blue or black jeans, just so that they're nowhere close to loose, but not extremely tight either. I wear band shirts for metal (I'm a big metal head) and rock bands, including AC/DC, KISS, Van Halen, Red Hot Chili Peppers, Green Day, Staind, Slipknot, Linkin Park, My Chemical Romance (they're alt. rock, okay? lol), and many more. I just like rock, and that's that. I play sports, and I don't dye my hair or have any piercings or make-up. Maybe I'm modern punk, or modern, refined goth, but NOT EMO.