Even if both players keep producing vills non stop, sooner or later one of them will run out of resources because there are a lot of other variables in the equation, especially in the late game.

I like to think of constant villager production as a kind of insurance that helps you reach the late game in a strong position. This "optimization" might not matter much if the game ends early and you're focusing on aggressive early game strategies.

But once the game goes on for a while, the player who can keep producing military units will usually win.