I'm also a guitarist, so let me try to explain why a relic'd guitar can be a good thing.
Very often, guitars, particularly ones with polyester finishes, feel stiff and cold when you strap them on, almost too perfect. They don't feel player friendly. A tastefully relic'd or aged guitar often feels broken in, comfortable, like it's seen hundreds of gigs already. It's been well played and is user friendly the minute you put it on, and that's why players like myself like them. They just feel better than a shiny, plastic covered guitar. You hold a guitar against your body, so it's got to feel good. You don't do that with drums.
What I have a problem with are amateurs who take a belt sander to a perfectly good guitar and ruin the finish. When relicing is done by someone who doesn't know what he's doing, the results are usually terrible and laughable at the same time. You see them on Ebay and Reverb all the time, and you can always tell the good relic jobs from the bad ones.
I hope I've explained why some guitarists like relicing. Another thing: some people say you should only relic a guitar naturally over a period of time, say 20 or 30 years. Well, some of us don't have 20 or 30 years to do that!
Finally, John Mellencamp's drummer, Dane Clark, uses a relic'd drumset with rusty hardware. Check them out online sometime. I'd say 98%% of the drummers out there want their drums to look bright, clean and shiny, so I doubt the relic thing will ever happen to any extent on drums.
