Copyright law is precisely a means to an end of encouraging more works to be created (and thus eventually enter the public domain) and absolutely nothing else. In particular, compensation to the creator is nothing but a proverbial "carrot," not any sort of moral right or entitlement.

It's also a power of Congress, by the way, which means it's optional. Congress may enact copyright law if it so chooses, but is not obligated by the constitution to do so. This is in stark contrast to e.g. the Bill of Rights, which is written the opposite way: presuming such rights exist and prohibiting the government from infringing upon them. In other words, if the framers meant for copyright to be an actual "right," they clearly would've plainly said so!