Well, it's something that's been done for the Lascaux cave and more recently with the Chauvet cave in France, because allowing the public in the real caves woul

Well, it's something that's been done for the Lascaux cave and more recently with the Chauvet cave in France, because allowing the public in the real caves would damage the paintings on the wall. So if the integrity of the work is at stake, it's definitely something that might be done. But museum visitors are kinda like collectors but with less money: they want to see the real thing, not some cheap replica they could buy to put in their home. Museums don't exist only to teach about art and its history, they exist for people who want the experience of seeing the real thing without being millionaires. Even though most people wouldn't see the difference between the original and the replica and would be subject to some sort of placebo effect if they think the replicas are the originals.