The justification is that it's supposed to protect the individual creative from more powerful publishers just taking and copying their stuff. In practice, it seems to mostly protect the interests of the most powerful party.
> The primary purpose behind copyright law is to foster the creation and dissemination of works for the benefit of the public. By granting authors the exclusive right to authorize certain uses of their works, copyright provides economic incentives to create new works and to make them available in the marketplace.
https://www.uspto.gov/ip-policy/copyright-policy/copyright-b...