Tourism has to be managed. Most istitutions can't, or can in a relatively limited manner. Rich people provide both the money and the reputation to allow them to have profitable private tours without risking too much. There is no real reason why a museum can't be open at 2 A.M., it's just that it's economically impossible, unless someone pays enough money. There is no real reason why a small church painted by Giotto can't be opened to the public, but managing all the people and making sure they don't damage stuff is a nightmare, unless the people entering have a verifiable reputation.