There are 2 other problems - first so many think that a UAV is just for ISR/ISTAR when it can do so much more. Second it quickly becomes apparent that a UAV can do 90%+ of the current FJ AG role, whereas the FJ can only do 50% of the UAV role and the UAV can be on task for 10 times as long for 10% of the cost. At that point some people get very defensive about their shiney pointy toys.
Not suggesting that UAVs are totally capable of replacing manned aircraft - not for a long time.