It seems to you that you know very well how to play at Blackjack and be successful in it. But the reality indicates at other things. A lot of mathematicians count several variants that are used by Blackjack players. And look at the result:

-    Never to surrender: the player, buying in, thinks that he gets 10 points. As a result by 12 points and higher the players don’t buy in. This strategy increases the house edge till 4%.

-    Repeat the dealer’s actions. The player plays according to rules of the dealer: he or she buys in till 16 points. In such a situation the players loses the possibility to double up and split cards, as a result the house edge increases till 5, 5%.

-    The dealer has a closed 10. The player thinks that the closed card of the dealer is a 10, that’s why he or she buys in till 19. Such a strategy deprives the player of 10% advantages.

Counting cards: Blackjack offers players the unique chance to move up from the house edge to the player’s advantage i.e. to increase the expected value higher, than 100%. Such an opportunity is based on the idea that the pack, full of 10-s and Aces, is profitable for the player (there are more chances of dealer’s getting bust). Thus, if in the beginning of the game a lot of small cards have come out of the pack, then chances of players increase.
Card counters always wait for such a possibility. They count cards that have come out of the game and if they see, that in the pack there are still a lot of pictures, begin to increase bets, trying to make profits from high expected value.

But such a theory can also lead to failure, as at online casino the pack is always mixed after each deal or the endless pack is played.