This is the issue - you can program a computer for every conceivable problem, and combination thereof. Then a problem occurs that no-one conceived of and the computer has no answer, what then? You need a human with the experience to solve the problem there and then, and the computer to fail safe and help out when required.
Anyone who thinks a computer can be made to cope with every possible situation is deluded, and when failure means likely death you can't just wait and "turn it off and back on again".
Maybe AI may eventually have the answer but it's a long, long way off yet.