Two excerpts from From 'How Airliners Fly' by Julien Evans:
The debate continues, as it has done for the last few decades, as to the degree to which pilots should allow the ever more capable automatic systems to take control. Should the aircraft be allowed to fly themselves with minimal pilot input in order to maximise precision and efficiency? But will this policy reduce basic piloting skills, which might be demanded when the automatic systems malfunction, or when circumstances arise which are beyond their capabilities? The human mind brings to the flight deck the element which machines and computers lack - judgement.
Will pilots be able to fly their aircraft without the assistance of autopilots and autothrottles when necessary if they never get the chance to practise these skills during normal operation? A related factor is that a pilot whose job is merely to watch the aircraft fly itself is unlikely to be as well motivated as one who can get their hands on the controls now and then. Designers of aircraft and airline managers must address the issue of how much and under what conditions pilots should be allowed, or indeed encouraged, to fly their aircraft manually. It is likely that compared to a mere aircraft monitor, a skilled, motivated pilot will always make a greater overall contribution to flight safety.