Well, if he did, he'd angst for days and days. And I don't like to see Naruto angsting much, because Sasuke is already an angster and so are much of the Tragic Bishounen Posse. I agree that Shikamaru would kill, if it was strategically necessary. There also is less killing, probably, because of the need for recurring characters.

Although with the latest manga arc, all bets are off on death mode.