Everytime Sasuke said it Sakura had just before it said something ignorant. Made fun of Naruto for being an orphan, changed her reasonings in a spur of second showing she was not genuine (and taken her own family for granted) and told Sasuke things can go back to the way they were when he had just said he wants CHANGE. It's not a compliment or endearment. Note how for Sakura it was said during negative moment when Sasuke genjutsud her, while for Naruto he said usuratonkachi after they reconciled. Kishimoto wasn't exactly subtle with his writing of Sakura.