Why is internet needed for Museum Mode?

F13's cabin was playable without an internet. Why does Museum Mode need internet? It'd be nice if this was changed as:

1. It'd be a simple and (hopefully) easy change

2. Guarantee we can always revisit the game if the servers were to ever shut down (right now if servers shut down, Museum Mode and solo Custom Games would be unplayable along with multiplayer, leaving the game 100% inaccessible to ALL players)