Sasuke and Sakura are both more liabilities than assets to the village. Sasuke is prone to fits of jealousy, and is more loyal to power and revenge than to his village. His judgement is easily clouded. He's also more of an asshole in general, especially after his encounter with Itachi.
And it seems to me that after the Chunnin exam, the other gennins are always chasing after Sasuke's lone wolf actions. The first time was trying to find Sasuke who went after Gaara (well in this case maybe I'm wrong, maybe Sasuke was ordered by a Jounin to chase Gaara). The second time was when Sasuke left to find Orochimaru.
Of course Sasuke is still redeemable, after all the author can just claim it was all because of the cursed seal, who was consuming his soul and breaking his free will. But maybe the author won't redeem sasuke, because sasuke might make a better villain.
Sakura is just worthless, everytime she's on a mission, she's worse than useless because she's often in trouble, putting her teammates in bad positions trying to save her. She has no tactical skills, she has no special technique. The only thing she seems to be good at is explaining how chakra systems work, and dispelling sleep. She definately is not even good at looking through most illusions, she was fooled several times.