But the bootlegger is taking a copyright protected work and copying and distributing the work for profit without the authorization of the original copyright holder, thus cutting said holder out of any financial gains/royalties. Perhaps the bootlegger legally purchased his own copy in the store, but once he begun making copies for distribution, he "packaged" copyrighted works he had no authorization to do so...

And what about recordings the artist/record label had no intentions of releasing, but still find their way into people's hands/hard drives, like live shows or demos? That is theft...