What happens when someone interrupts the wireless signal between pilot and machine? Iran managed to hack a US drone and bring it in...
Second best case, the UAV detects the loss, resorts to on-board autonomous programming, goes into a holding pattern for some amount of time while attempting to reacquire the signal, then aborts and returns to base.
Bad case, the UAV without human intervention is a sitting duck and gets shot down.
Really bad case, the UAV can't detect that it's command net is compromised and the enemy directs it to RTB and attack there.