Because they are snobby gatekeepers who think making art more accessible would dilute their value. These sorts are very common in the art and academia world.
I read it like this: the museum wanted to safely preserve the original so they made a digital copy and hid it in a drawer. The author pointed out this was not lawful, and the museum panicked because they intended it as a digital copy protected similarly to the original. So, commendations to the appeals court for identifying the key philosophical issue; regrets that they ignored the actual law.