It's a matter of money. Many rail museums would love to own all their property. Most rail museums do not have an extremely wealthy person as a member who is willing to buy a railroad and donate it to the museum. So the museum group has to lease or rent whatever property it can. Or in some cases make an arrangement with an existing railroad or local government. Without a way to get use of land at a very low cost, the museum would not exist.

A problem for operating museums is bringing in enough money to maintain the track. I've seen some museums and tourist trains operating on very marginal track. The Maui Sugar Cane Train recently spread the rails and the locomotive fell in. Fortunately no injuries or equipment damage but it was going only about five mph.