Bootlegging is copyright theft. Whilst they may not have stolen your money, you actually gave it freely, you are or were buying illegal copies of music, no copyright was paid, no royalties to anyone due them etc etc. As said earlier bootlegging isn't just unreleased or live music, it is the distribution of anything unlicensed. I think that is what others are intimating.
I agree entirely it isn't the same as what is happening here and elsewhere, counterfeits, done to look the same and to defraud or deceive people.