Yes, market value is probably not the term we want to use to make statements about what should be done around copyright law. Anything you can't force people to pay for has no market value. Making a normative statement about whether people should have to pay for something based on market value is begging the question.

It's more important to think about utility, because that can help us answer the question of whether the government and laws should be used to create market value where there is none by trying to make a good excludable.