Knowing the true count when counting cards is important because it provides a more accurate measure of the deck’s composition by adjusting the running count for the number of decks remaining. This helps players assess whether the deck is rich in high cards (which favors the player) or low cards (which favors the dealer). A higher true count allows players to increase their bets and make better strategic decisions, such as hitting, standing, or doubling down. Without knowing the true count, relying solely on the running count would lead to less effective betting and play.