As with many things in game design, the objective with this random value is to make sure that we have enough of it that it’s doing the job of randomness, but not so much that it is the thing driving the car. We want the player to be mainly driving the car; we want the final outcome to be a pretty darn clear result of the player’s inputs throughout the match. We don’t want players to have to play five, ten, or more matches to figure out if they’re really winning or if it’s just randomness swinging their way.

Source: Randomness, and “Random Value Absorption Thresholds” – KEITH BURGUN GAMES