Andersp:  Backgammon is not a luck game; it is a skill game with a random component.  A large part of the skill in backgammon is understanding and working with the random component.  However, it frequently happens in a single game that luck overwhelms ths skill component, and a lower rated player wins because of having better dice rolls.  The chances of this happening diminish as the length of the match increases.  But in a single game, a very good player can expect to lose to an average player 25-35% of the time.  This would be unheard of in chess, on which the ratings system here is based.