Copyright is inherently a restriction on the free market. Unlike physical goods, writings and recordings can be multiplied and redistributed by whoever possesses them. Copyright was originally a way to ensure authors got a cut of the revenue stream when their works were republished. Thus, publishers were required to pass on a bit of the cost of each book (and later recording) to the owner of the copyright, resulting in higher prices to the consumer. Without copyright, prices for all works would be lower, but the creators might not be inclined to produce without the compensation provided by royalties.
In the United States, the power to grant copyrights was explicitly included in the Constitution and exclusively granted to Congress.