Spore doesn't have a story, It's a sandbox.
Is it? Because in my game, the game keeps making suggestions on what I should be doing. Like, right now, it says "go find the Grox". I don't care about the Grox at all. So, if there is no "story" to the game, why does it send me there? And why does it send everyone else there and everyone's game includes the same evil alien empire?
There certainly is a story to the game. You aren't pressured to follow along with it very much, but clearly there is a series of things you are encouraged to do. In Cell, it said unlock some parts. In Creature, it was migrate to the next nest. In Tribal, it was deal with nearby tribes. In Civilization, it was unite the planet... the story is the story of your creature.