Because having people download static map data for the entire planet just to play a game is untenable.
You shouldn’t have to download the entire planet though.
The game 100% should support installing local specific areas you wanna fly around, that anyone could then keep a copy of.
If a user wanted to cache an entire 8 TB of the entire world on a drive, they should be able to just do that (and thus have forever support without worrying about internet services staying online)
At least, as a snapshot of what the world looked like in 2024.
I don’t see why users shouldn’t have the option to locally HD save the data if they want to, to avoid maxing out their internet bandwidth in one sitting.
You do cache what you use as you use it
The issue is with this being a forever game. If there are no servers there is no streaming. Hence the need to somehow host a one off entire world download indefinitely.