7 string for metal band guitarist? Hekekeke... well, why dont the BANJO have 7 string too? The naturality is the key to this answer... it depends on individuality... assume Steve Vai play for Metallica or maybe Limbizkit, or maybe Ozzy Osbourne. U can see that, it depends to the guitarist, whether he can play with 7 strings and say u tell a metal band to play with 7 strings now, it shall take times for them to adapt to 7 strings although theres not much big difference in the theory with 6 strings. Well, the exact answer to this is, because... the guitarist does not know how to play with 7 string guitar and vice versa. Dont expect all good guitarist are born to play 7 string guitar. Even the best guitarist are born to play 6 string at the first place. 7 string is UNIQUE. Imagine all band.... not just metal band.... all the guitarist can play 7 string.... now this is a situation where Steve Vai does not want to see... but of course he is the one who invent the guitar and produce this 7 string theory. What about the others who can play 7 string? Hehehehe.... u might not want to hear all guitarist can play 7 string...not just u... thats why 7 string is unique and let the Unique minded people learn how to play 7 string guitar and see how unique the may be.....