The following variation in the Tarrasch French Defense has an idea that might be counter-intuitive to weak and strong chess players alike. White spends a lot of time moving his knights in this opening setup. His queen knight hops from d2 to f3 while the king knight goes from e2 to f4. One of the reasons a white knight wants to land on f4 is to inhibit f6 which would leave the Black e6 pawn hanging . Pawn to f6 is a very common reaction for Black when White advances his pawn to e5.
As John Watson points out in his French Defense book, much of chess is information theoretic. What sort of information do your moves provide to your opponent? Although Black castling in the pictured position is probably not bad, unwinding the Black forces on the queenside is likely a better course of action for the second player. The sequence of moves Nb6, Bd7, and Rc8 and then perhaps Kingside castling provides less information to White about Black’s intentions. John Watson writes about the avoidance of providing too much information, too early to your opponent in a chess game!
The move Nb6 looks like it might invite White to react with a4, but this would give up the b4 square which could be effectively occupied by the Knight at c6. Nb6 also clears d7 to be occupied by the Achilles heel French Bishop which, in turn, frees up c8 for the Black Rook.
This uncoiling of the Black Queenside is very similar to some variations in the Sicilian where the Black King remains in the center while Queenside development is transpiring. It is useful to note that castling early is NOT tantamount to King safety. In fact, castling too soon can make your King an early target in a chess game since you are providing too much information to your opponent. When the center is closed, do not be in a big rush to castle. Consider wing developments that might give your opponent a few things to worry about!