Right, the doubling cube is what sets apart the good players. For every possible state, there is an expected value of your outcome, from the current state aver

Right, the doubling cube is what sets apart the good players. For every possible state, there is an expected value of your outcome, from the current state averaged over all possible continuations of the game or match, if you make perfect moves and your opponent also does. (This can be denominated in either cash/points value within one game, or in expected match-win value across a match of multiple games.) The swing of backgammon is in the imperfect moves, and in how much expected value each one costs you. It's not that hard to study checker strategy well enough that you're rarely losing more than 1% or so of a game's value; even if you make imperfect moves, they're generally still pretty good. But the doubling cube can account for much greater swings; a mistake like doubling too early or incorrectly responding to your opponent's can easily cost 20% equity or more.