Face it...a modern jet, say 757, could really be flown by one pilot.
but you lose the second pair of eyes. the redundancy in case of pilot incapacitation is lost.
and why not change to a one engine plane. ?????
I recall when the local subway system, known as BART was introduced. Completely automatic...no train operator was to be required.
and it didn't work out that way...and they put a driver in each train.