Why do people think metalheads are one-dimensional in terms of musical preference?

metal is a very diverse genre. you have thrash, heavy(my 2 favorite) death, viking, black, folk, power, and then shiit metal. metalheads usually like clical music as well as rock, and maybe a TINY bit of rap. i tend to listen to thrash mostly, but i will listen to punk, rock, and a tiny tiny tiny bit of rap (6 songs out of 900)