vilas
Consider that pilots, potentially, while bot error free, commit different kinds of errors and have the capability for creative problem solving. They are not preprogrammed computers limited to actions and reactions thought of ahead of time. Think of Sioux City, Hudson River, Gimli, etc.
For all the money presumably saved, consider the cost of a single catastrophic accident. When things are working normally, the automation can perform more efficiently and in some cases with higher performance. But not so win non normal circumstances.