You mention that you are surprised that these drones are not already used that way. Well they are used that way now by state-sponsored Jewish terrorists (IDF) in occupied Gaza. They are NOT, however, used by maniacal people with a vendetta against humanity. That imagined threat is almost 100% state propaganda, and is the narrative of choice when pushing for totalitarianism. Reality about human nature is not so bleak, it is not something we have to over-prepare for.
So people aren't motivated to be wanton killers. There just aren't any motives for it. On the other hand, the state absolutely has very clear motives: profit and legitimacy. But if killing becomes super cheap, the profit motive goes away, because you don't need an expensive military industrial complex to build cheap drones. However the other motivation of state legitimacy remains as long as people give power to the state. The state needs enemies such as (false flag) terrorism to justify its existence.