Because it used to be that if you wanted to kill someone with a missile you had to figure out their location with a man on the ground, then fly a half billion dollar war machine over their house and hope you can hit it while flying 1000 miles per hour. Also hope that your target is still there, because this half billion dollar war machine took six hours to fly there from its aircraft carrier (which itself a hundred billion dollar war machine that you have parked off the coast of Yemen just so you can off a couple of middling priority targets)
Now you have a 10 million dollar war machine that doesn't need a pilot, can be launched by an agent from anywhere, and which is equipped with a camera so you can do target acquisition on the fly. In other words the game has changed from "there's no way you're ever going to be able to kill someone like this, and you'll waste a trillion dollars trying" to "yeah we kill people like this all the time, and it costs about a million bucks a pop"