Drones have seconds of latency, which is a time delay between the sending of the control signal and the drone’s response. This is why drones need to be autonomous; they need to continue doing what they were set to do for a few seconds without instant intervention from the ‘pilot’.
That is also why the missiles drones fire have targetting capability. The target is locked into the missile’s computer before the missile is fired. The missile then guides itself to whatever it was locked on to, without intervention from the drone or its ‘pilot’.
Jihadists are cheaper and more reliable, especially in 2001.
Of course jihadists think of themselves as holy warriors, not terrorists, and they have been brainwashed from birth that (1) if their mission is God’s will, God will help them accomplish it and (2) they can commit any sin before a suicide attack and it will be forgiven for their self-sacrifice. The hijackers behaved exactly like jihadists.