Originally Posted by
Stormcall
It happens with most genres. In metal for example you have classic/traditional/"heavy metal", power metal, speed metal, thrash metal, prog metal, death metal, black metal, doom metal, stoner metal, metalcore, glam/"hair" metal, hardcore, nu metal, rap metal, goth metal, industrial metal, folk metal, grindcore, then you branch out into the sub-subgenres and the hybrids you get power-thrash, blackened death, doom-death, melodic death/melodeath, "viking metal", tech death, blackened thrash, "epic doom", power-prog, deathcore, mathcore, symphonic black metal, symphonic power metal, funeral doom, etc etc etc.
Some of those shouldn't exist as a label at all(looking at you, viking metal), but there you go.
And yes, sometimes it can be helpful. If some dude says "I like metal give me some new bands to try", because he heard Blind Guardian, Gamma Ray, and Hammerfall and liked all of them, chances are good he's not looking for Cannibal Corpse, Nile, and Bolt Thrower. Now if he says "I like power metal, give me some new bands to try", I have a much better idea what he's looking for and what to suggest.