Or we could create a new system, one not based on the idea that you can own math and poetry, one not based on promoting the interests of publishers, and one that instead encourages the sharing of source code. The GPL is just a way to establish such a system by using the existing approach. There is no reason why we could not scrap copyrights (at least on software) and write a law that codifies the GPL more directly -- say, that any software user has the right to request a copy of the source code for their software.

I'm not saying it is a realistic possibility in today's world, but it is not as though the copyright system is the only system we could have.