Why does every game, no matter how good, always have at least one 0 score on metacritic?

Is it because they felt the need to be a total killjoy? Want to look different by saying "Hey, all these people are playing a SUCKY game!"? Oh, no, there's exactly ONE reason you rated this "otherwise fantastic" game a zero? Sure, Portal 2 sells you optional robot hats. Who gives a **** about silly sheep things like "gameplay" or "story"? We've all obviously been waiting 4 years for DLC hats, and you've let us down, Valve.