[Autopilot takeoff is trivial compared to autoland. I first took part in autolands with pax on board 50 years ago, but 3 aircraft generations later no-one has built a commercial aircraft with an auto takeoff system - there's no business benefit to doing it.]
Isn't the real reason, takeoffs are optional, landings are mandatory
Serously, just look at the accident record to date. Military drones are operating with about ten times the mishap rates as fighters. Neither are quite as good as general aviation.