Take the Celtics/Knicks game last week. Boston made 21 free throws out of 21 attempts, winning the game by two points. If they had shot only 18/21 (85%) at the line, they would have lost.
So many close games can be won or lost at the free throw line. Which side of the win/loss ledger a team finds itself on can depend on how much emphasis they place on the importance of excellent free throw shooting practice.