In the museum case, the preservation role is explicitely asked for. It is one of official reasons for muaeum existence.
And in natural history museums their primary purpose isn't to show little Jimmy a T. rex skeleton but to preserve the fossils and other specimens for scientific research.
Not exactly. If this was the sole goal then there wouldn’t be a museum at all.
The museum literally exists because they’re expected to display some things.
The preservationists who fight against showing anything wish the museum part didn’t exist. They want it all to be a big warehouse where nobody can see anything.