There are two types of flying: instrument flight rules, and visual flight rules.
IFR is used at night, when the weather restricts visibility to under a certain amount (thick cloud cover can do this, no precipitation needed), on flights long enough that you can't guarantee VFR conditions at your destination, and just whenever you feel like it.
VFR is generally only used for beginning pilots or quick flights. It's sometimes seen as a relic of earlier times. Sure, you get taught how to fly this way, get taught some basic dead reckoning techniques, but nobody really flies this way, most of the time.
But instruments fail. Autopilots fail. Engines fail. When everything fails, you want someone in the cockpit who can look out the window, navigate by landmarks, and if necessary put the plane down on the straight sections of highway Eisenhower built to accommodate bombers returning from the Soviet Union.
When things go wrong, you want something smart and adaptable in control. There are procedures for damn near everything in aviation, but there's still things you can't pre-plan for. Until we get a general strong AI working, the only thing smart and adaptable enough is a human.
Now, that doesn't mean we can't have fully computer-controlled aircraft. It just means there shouldn't be people on board those computer-controlled planes. Drones are fine - even if it's a cargo-laden drone version of a 747, the loss of life it can accidentally cause is miniscule, compared to even a small passenger plane.