The story defines the game world, and therefore the entire game. It is there 24/7, 365 days a year, 2.x years each expansion.
Without a story, you could run around as a blue sphere and shoot white spheres at huge red spheres to earn pink spheres which you take to a spheric merchant to increase your sphere's 5 base stats: Mass, Traction, Surface Type, Spin, and Core Energy.
Only the story gives a meaning to this stuff, that's why nothing is more important than the story.
At least that's the way I see it.