The astute blackjack player pays attention to the house rules set by the casino or online casino for their blackjack games. This is why you do not see professional blackjack players playing variations of the game or at blackjack tables with poor house rules.
One such house rule that is of poor quality is allowing a dealer to hit a soft 17.
While on the surface this house rule does not like it would be all that damaging to a player’s blackjack odds. Many players assume that the dealer will just hit to busting. They make the mistake of assuming the dealer will still bust because he is starting at 17.
But what these unknowing players forget is that an Ace is just as flexible to a dealer as it is to a player. This means that if the dealer hits his soft 17 and receives a card that would normally bust a hard 17, he can reduce that Ace from being worth 11 to being worth 1, just as would happen for a player. Reducing the value of the Ace makes what was a soft 17 into a hard 6, which the dealer can then safely hit again and again with the possibility of stringing out a multi-card strong hand.
Because of that possibility, a dealer who is allowed under house rules to hit a soft 17 decreases a player’s blackjack odds. The hit to the player’s odd is for 0.22%, which is about half the value that basic strategy reduces the house edge to. So even with basic strategy reducing the house edge to 0.5%, a dealer hitting a soft 17 alone can raises the house’s edge back up to 0.77%–half the work of basic strategy is undone!
Now you see why blackjack professionals will avoid playing in blackjack variations and at tables that allow the dealer to hit a soft 17—they value their blackjack odds too much to throw away 0.22% of them.