Well art isn't just the artifact but is also the context that artifact is in. Certainly King Tut's sarcophagus is a great work of art (in a sort of ceremonial, religious way) and a perfect replica would also be very impressive, but would not mean the same thing as the actual place where Tut's body was actually placed.
The Mona Lisa is an example of this, one of the reasons for it's incredible fame is that it was stolen from the Louve, supposedly by Picasso. Certainly there are other works by De Vinci that are greater works of art but the fact that it was stolen from the most famous art museum in the world adds to it's significance and it's lore.
This is why people want originals and not perfect forgeries. They want the context that comes with the art and not just a perfect visual representation of the thing.
That being said there is something to gain from both a famous artists abstract renderings and a child's playtime. What those thing are is very different and that is why it matters, because art is more than the artifact.