Why do Melodic Death Metal bands use ultimately stupid and disgusting spooky vocals in their songs?

For example. Kalmah, Children of Bodom, Chimaira, Nightrage.. etc.
Their music usually sounds cool, however when they start singing, the only thing I will can do is stopping the song and deleting the entire album completely.
Do they ever listen to their own songs? And if they do, do they REALLY think they sound cool?

Or is it some sort of a satanic ritual? (because if it is, then that’s a good reason for me to quit listening to melodic death metal for good).

The only exception is Dark Tranquility, though.