Raina
Cineva de undeva.
I don't think there has to be a connection to goth rock, as even without that genre, gothic can still refer to literature, architecture, photography (etc.), and I believe it's still possible to incorporate this form of gothic into other forms of music. Image-aside, Cradle of Filth did this very well for years without having any real goth rock influences present in their music. However, I don't understand what makes 99% of "gothic metal" bands "gothic".
I believe it is the melodicity,poppyness,fancy-romancy lyrics, operatic vocals: women- soprano, man- tenor/bariton and eclectic clothing that define gothic... when it fullfills these criteria, then it is categorized as 'gothic metal'.
Though, I can see why these bands don't really sound very similar to old gothic bands (imo gothic rock sounds really close to pop/punk music, than anything else). But then again I only listen to some Sisters of Mercy and heard some Bauhaus...