In theory, a drone can operate autonomously, it's a question of how much we trust it to do so, and the guidelines programmed in to follow the operator's intent.
We need a connection to see what it's doing and what direct feedback, especially for realtime reconnaissance, updated instructions, and currently, remote control.
Three reasons to have to have a human operator is because we think we're better at assessing a situation, we want to know what's going on, and if it's armed, we decide if it should be triggered.
There seem to be two aspects of remote control, direct sensory feedback from the drone, and second hand feedback, or third party viewpoint, which would be the skill aspect in controlling a drone, in either case, understanding latency in receiving the feedback, and in carrying out instructions given by the operator.