Because Pakistan is a friend in name only. At least, that's the probable behind-closed-doors justification. And because we have no HUMINT in Pakistan and never will. And because drone strikes come out of the CIA budget, which is under congressional seal, and are carried out under the Espionage Act of 1917, whereby unlawful disclosure is a violation of Title 18. So when we use drones to target people in Pakistan, it's black money with no oversight against a country that's been widely regarded in intelligence and foreign policy circles as an unabashed enemy since the death of Zia al Haq in 1988. Which doesn't make it "okay" but certainly changes the narrative. I mean, it wasn't "okay" when we were dropping napalm on North Vietnam either but the public narrative and the private one weren't so divergent.