Yeah - sorry to be harsh , but I have strong felings about the guitar having evolved to match the range of the human voice.
This is one of the reasons that we can find some solos etc emotional as they are using similar notes that occur in humans when upset or euphoric.
Taking things lower with 7 strings was maybe an interesting departure, and 8 was really for guys wanting to explore subsonic territories, but it is proving very difficult to find singers who can sing as opposed to grunt or shout over songs(?) writen and based around such detuned motifs.
It does get into a silly "my band is more metal or brutal than your band" thing, and without much sense as few cabs handle the extra low end and most club's PA systems wouldn't handle it well.
It'll certainly piss off parents - - so maybe that is the only incentive that teenagers need to love it, as it must be way harder to annoy parents with your music if they grew up listening to punk and metal.