Ability to keep track of high cards relative to low cards that are being played. When the deck is rich in high card you should bet more - when the deck is rich in low cards you should bet less. Since the dealer has to hit his "Stiffs" 12-13-14-15 and 16 when the deck is rich in high cards he will bust more. When the deck is rich in low cards he makes winning hands from his Stiffs. Also, "significantly" the player gets paid. 3-2 on Blackjacks and the dealer gets paid even money. Also, when you split and double down (the dealer cannot make these plays) you usually want high cards.