I doubt there is another table game out there that has as many variations as blackjack has. It is played with anywhere from 1 to 8 decks. Blackjack might pay 3 to 2 or 6 to 5. You might be able to split to 2 hands, 4 hands or maybe more. You can double on any two cards you want or you might be limited to only 9, 10 or 11. The Dealer may hit on soft 17 or he may stick on all 17's. Why so many variations?
In my mind, there are two reasons. The first is that each of aforementioned options effects the payback of the game. Some by more than others. The biggest impact is probably paying 6 to 5 on blackjack instead of 3 to 2. This reduces the payback by about 1.4%. While the difference between 98% and 99.4% might not seem all that big, I prefer to think of it in terms of loss rate - 0.6% vs. 2%. The loss rate more than triples. Now it seems a lot bigger.
The second reason is that each of these subtle changes creates slightly different strategies. More strategies for so many different versions means that the average Player is going to eventually get these strategies confused. Each time a Player plays the wrong strategy on a game - or more aptly the right strategy but for the wrong version - he gives up a few tenths of a point of payback to the casino.
A perfect example of this is the option of the Dealer hitting on soft 17 vs. sticking on all 17s. This creates both a higher house advantage and a slightly altered set of strategy decisions. When all is taken into account, the impact is just over 0.2% of payback. Not nearly as big of a deal of paying 6 to 5. But, it still increases the house advantage by about 33%, from 0.6% to 0.8%.
This particular option is a well thought out one. I'm guessing that many people don't even realize that it increases the house edge. It is sort of a "glass half empty or half full" type of option. When the Dealer has a soft 17, he has both the chance to improve the hand or bust it. If you don't know how often he does both, then you might struggle trying to figure out if it is an advantage or disadvantage for the house. While the Dealer might bust what otherwise would've been a 17, you have to keep in mind that a 17 is NOT a strong Dealer hand. He beats everyone who stuck with a 12 through 16, but loses to all the Players who wind up with 18 through 21. The Dealer was going to beat anyone who busts no matter what, even if the Dealer goes on to bust himself.
There are not a lot of changes made to strategy because of soft 17, but there are a few. As should be no surprise, NONE of these changes occur with a Dealer upcard of 7 through 10/Face. The Dealer cannot have a soft 17 with these upcards, so there is no impact. The most common upcard for a soft 17 is an Ace and that is where we find most of the changes. If the Dealer has an Ace and the Player has an 11, he should double down if the Dealer hits soft 17. The reasoning here is that the Dealer has a greater chance of busting when he hits a soft 17 and this is a major factor in doubling down. Two other changes when the Dealer has an Ace is that the Player should Surrender when he has a hard 15 or a hard 17. (he already Surrenders a hard 16 even if the Dealer sticks on all 17s). The hard 15 and hard 17 expected value decreases when the Dealer hits a Soft 17. The strength of the 17 is normally the Push, but these greatly dry up with the Dealer hitting the Soft 17. The hard 15 is a weak hand no matter how you look at it. While the chances of the Dealer busting goes up, he also increases the chances of winding up with an 18, 19, 20 or 21. This is just too much for the hard 15 and it now pays to Surrender.
In similar fashion, the final change when the Dealer has an Ace is the Pair of 8's. This actually becomes a Surrender situation. Splitting is normally the play. but with the extra strength of the Ace, the Player is better off giving up half of his weather.
The final two strategy changes are Double Down situations. In both cases, the Player should now Double Down when previously he would stick. The Player should Double a soft 18 vs. a 2 and a Soft 19 vs. a 6. If you Double on a soft 19 and wind up with garbage, the Ace as a down card no longer becomes a sure loss, but rather you still have a chance that the Player will bust, turning your losing hand into a winning one.
All things considered, you're better off finding a game where the Dealer sticks on all 17's. But this simply may not be an option. In which case, you need to be prepared with the right strategy and a knowledge of what to expect.