This goes back to the original purpose of copyright, which is to serve as an economic incentive for individual creators and artists to make more art, by securing exclusive rights to use their own works commercially for a specified time. The goal is both the creation of more works, but also to protect the economic viability of artists.

This principle is quite universal and can be found in many places, including the US constitution and US (supreme) court decisions, many international jurisdictions, treaties and conventions.