There is no easy answer when it comes to the question of whether or not the casino always wins in blackjack. While it is theoretically possible for a player to lose money at the casino by playing blackjack, in practice it is exceedingly rare for this to happen.
In fact, most players who play blackjack will end up winning money overall.
One reason for this is that, even if a player plays poorly, the casinos usually have enough good hands to ensure that they will still end up with a profit overall. Furthermore, casinos have developed sophisticated strategies for dealing cards which can lead to large profits even when a player loses.
In short, while it may be theoretically possible for a player to lose money playing blackjack, in practice this is quite rare and most players will end up winning money. This is because casinos have various strategies which can lead to large profits even when a player loses.
