For most musicians, isn't obscurity a much bigger problem than piracy? Sure they'd prefer that people bought the music, but if it's me I'd rather people listen for free than not listen at all.

At least half of my music collection is stuff that I never would have spent the money on without having downloaded it first. I have bought quite a few albums I downloaded first. I still have quite a few more I want to buy. I also have downloaded a ton that I'm glad as hell that I never spent a penny on because it flat out sucks.