Metal fans are some of the nicest people you will ever meet.
Pop fans are the crazy fucks that will trample you to get close enough to get hit by sweat from the stage and then shatter your eardrums when they scream with joy.
given the general respective ages of both crowds it makes sense, but if you think the crowds are completely silent at metal festivals then i think you're confused. and also taking into consideration the cacophonous nature of metal music vs. the more "delicate" (i use those quotes heavily) nature of pop music.
Pop fans are the crazy fucks that will trample you to get close enough to get hit by sweat from the stage and then shatter your eardrums when they scream with joy.