More than that, if we grant that the comparison is valid (which I'm not necessarily doing), I'd still expect Grod (a name I'm choosing for no particular reason) here to be compensated for the time and effort put into inventing a method for producing fire, instead of hunting and gathering. Otherwise, Grod is effectively being punished compared to his or her fellows. Also, this is patent law, not copyright, but I'll admit that in spirit it's fairly similar.
Replace the method with the idea of fire making, the analogy stands.
Grod wants compensation, and if compensation is what Grod needs to be motivated to create these fire making ideas then Grod should have this compensation.
Let's say Grod makes his fire. Sod wants to light a branch with Grod's fire. Sod is not taking Grod's fire away, but is making a new one that would not have existed without Grod's original fire. Grod demands payment of corn for allowing Sod to make this copy.
This goes on for a decade, with Grod living off this corn. Pod is looking on making a new idea, and fire is needed to help make it come to fruition. Pod doesn't go to Grod, but goes to Sod and makes a new fire from his one. Grod is angry, and says to Sod that a decade is not enough time, Sod needs to give Grod corn for compensation, otherwise Grod is effectively being punished. So he punishes Sod and Pod by sending them to prison and giving them a corn debt larger than what they'll make in a lifetime.
30 years later Grod has grown fat on his pile of corn. He's made a throne out of the cobs. He hears that someone in the neighbouring village has been showing other people how to make fire.
So he sends his hired Chieftains to bring him to his prison. Grod also hears of someone who is giving away charcoal so that many people have the ability to make fire. The audacity!
So he sends his Chieftains again. Grod, now very rich on corn has started hiring other people to make sure he receives his corn as well. He hears there are people using his fire idea to cauterize wounds.
Don't the fools know by not giving him corn they're stifling creativity? They must be selfish.
Grod hears that people are using his fire. They put it in furnaces and begin smelting.
But where is Grod's corn? Grod hears that people are sending things through a series of inter connected tubes. Grod thinks someone said something about fire there.
Shut it down. Some people say they were doing nothing that involved fire at all, but Grod gags them anyways.
10 years later Grod has created a fire empire. Everything that the sun falls upon, everything that combusts is his. His compensation. People go about cooking, careful to make sure they never so much as get a single molecule of oxygen in their heat or heat in their fuel or else they are punishing Grod and are going to have to pay corn or pay the price.
Grod dies eventually, but the people are still fucked because Grod still needs compensation 60 years after he's died.
The purpose of copyright is to compensate the creator.
The usage of copyright is to exploit the created.
The price of copyright is the stifling of creativity.
But the intention of copyright is to encourage creators to create.