Same reason we haven’t “proven” that bigfoot, the loch ness monster, or jersey devil are “bullshit”. In order to prove something, you need to find evidence for it. If there is no measurable evidence for something, that does not disprove it, it just does not support it.

You can make of it what you want, but you have to make the effort. There is a mission for base building, and mission boards for doing cargo, bounties, exploration, etc. The game does start out with the storyline, but it doesn’t force you to stay on the story past a certain point, you are free to go off and do what you want, but it also doesn’t hold your hand, and you have to figure out a lot of mechanics on your own.