People are making judgements based on the look of the instrument. With its double cutaway design and its sharp-pointed headstock shape, the original PRS looks radical in comparison to the more rounded, classic Strat, Tele, and Les Paul shapes. The fact that PRS's first mass-market model was a 24-fret guitar with very high-output pickups only adds to that perception. And to be fair, it seems like metal players really adopted the instruments en masse before anyone else did.
What's interesting to me is that I'm seeing a lot of country artists playing PRS these days, much moreso than mainstream rock/pop players.