Would it be technically possible to have a fully automated airliner, well most likely. Is it practically possible, not likely when you account for all the variables. And there are several tangents to that.
Technology integration and possible investment failure is a line of thought. In fact prematurely introducing a technology before it is mature enough can deal a devastating blow to its image and potentially cripple it for a very long time.
So along these lines. It is one thing testing, its another thing introducing it to the real world. We know for a fact that real world use can bring out all sorts of bugs and faults that should have been foreseen, and others that where not, and could not have been foreseen. Now we don't need to go though a list of aircraft models and faults do we?
The effect is, apart from the general apprehension associated with Jo public in the first place, what do you think is going to happen after the first one or two aircraft inevitable drop out the sky?
Automation on ground vehicles is still in its infant stages, and has troubles. The mining industry is trailing automated haul trucks, and they barely work. We have a long way to go before we have practical automated aircraft.