So, the government said: "We'll create a theory called "copyright" that means:
that creators have the exclusive right to make certain uses of their work for a limited time...
BUT anything beyond what we *explicitly* reserve for authors is granted to the public.
AND eventually, all of the uses may be enjoyed by any member of the public (in the public domain).
In a nutshell:
We give authors and their publishers rights to control *some of the ways* of exploiting their works.
The rest of the value is left to the public at large.