It would be far more effective to just add machine guns to UAVs like they do on the Apache [0]. It's simple, proven and effective. There is absolutely zero need for the bullets to be delivered by a crappy quadrocopter. You can send out quadrocopters for face detection and then just shoot people with the machine gun. This reminds me of that stupid missile that shoots blades. It's completely over engineered.
While I don't disagree with you, there is a very real need to avoid collateral damage in 2020. You cannot expect support at home if your drones are murdering a bunch of kids for each "bad guy" that they eliminate.
You want to be able to kill any leader anywhere and let the organization collapse due to internal power struggles. It's more fashionable.
[0] https://www.youtube.com/watch?t=629&v=vMylpfX7_S0