I don't think it
needs it. I just always find I'm utilising the extra headroom that the pog offers, specifically with the sub octave, and that other sub octave pedals where never that interesting to me as a result of only running at 9v. However, as erskin points out, that's comparing octave pedals, and not a sub octave fuzz, which I'm sure will be punchy enough for what it does.
Plus at higher gigging volumes I guess most people aren't going to push sub-octaves very high incase they mess their speakers so then 18v is going to be a rather pointless thing to have just to satisfy bedroom players like myself
It's not a "clean" octave pedal so the issue of headroom is kinda moot. It does have PLENTY of output level though (unity is around 9:30). And the Cut control allows you to not "mess with your speakers" when running it into a loud, cranked up amp.