"Make the information hard to get! We own it!"
Never realizing that sampling of the information makes it just that much more prestigious and desirable to us, the unwashed masses, willing to pay to visit a museum that has AMAZING ORIGINAL THINGS.
If you start with the assumption that every view is a lost sale, you're going to have a really bad time.
Outside of the Louvre and maybe the Smithsonian, there are no current world-famous museums, simply regionally or subculture-appreciated museums, some with bygone fame that a small portion of the older population would recognize. The Rodin Museum may be popular among a tiny niche slice of people, but if they were to make an internally consistent strategy that they want growth then they'd release more information.