Why do we use drones piloted by humans? Because guided missiles are expensive, dumb rockets are cheap, and drones (while expensive) are recoverable. We want someone empowered to cut and run, so that we don't lose the drone. At the distances that spaceships would need to battle, you need to use autonomous guided missiles anyway. The lightspeed communication delay would rather defy the point of any sort of remote-piloted drone.

Also because the guidance-in-atmosphere problem is much more difficult than the guidance-outside-atmosphere problem.