For some reason blackjack players believe that if a person deals the game, they must be an expert when it comes to playing the hands. This unfortunately is not true. Most dealers know very little about basic strategy and less about winning techniques like card counting. For example, taking even money on blackjack hands and to not split a pair of 8's when their face card is a 10 is just a sample of the wrong advice I have observed dealers offer players. The policy in most casinos discourages dealers from telling players how they should play out their hands.
Some friendly advice is OK especially if the player is a beginner.
But for the most part casinos discourage dealers to offer playing advice to players because they do not want to be put in the position of being blamed for a player's losses. There is also a security issue because in most instances when a dealer tries to cheat a casino it usually involves a fellow player as an accomplice. Dealers aren't the only ones giving misinformation to blackjack players. Always split aces. Double down on two card combinations of 9,10,11.