Why don't plane companies already put computers in their planes, are they stupid??
Oh wait, they do. And they still have expensive pilots, because the billions from Boeing, Airbus, Garmin, Lockheed, BAE etc. couldn't get it to be perfectly reliable [1] in all edge cases.
[1]: actually, not reliable enough. Risk assessment and management in planes is a super fascinating topic, the only risk-free plane would never move and cost 50 quadrillion dollars