Because having people download static map data for the entire planet just to play a game is untenable.

I’m certain Soviet General Staff maps turned into a flight sim map, with a few thousands of buildings being modeled and textured individually and the rest with similar (like buildings made of hexagon modules in some games have variety, but the separate components are not too numerous) procedurally-generated repeated kinds of meshes, textures and shaders, would take weigh little enough that you wouldn’t notice download times.

What else do they do for flight sims?

Weather data? A lot, but not that much.

I just can’t imagine what would need 64GB. I think it’s an intentional waste for the purpose of this game not being playable after its end of life.

A bit like Heinlein’s “Door into summer” future economics. Only there such stupid things are done to reduce unemployment, while here they are done to keep markets predictable for corporations and controlled, so that they wouldn’t, you know, die, as they would in a normal market because of competition.

Which reminds me of one important thing I’ve already changed in my life to not support such malicious actions. I don’t buy products that are intentionally made this way.