Still those technological issues do happen, and in those situations it's good to have a human pilot in control. See for example Qantas Flight 72 - the autopilot thought aircraft was stalling, and sent the plane into a dive. It could have ended up very badly without human supervision.

and then you have Air France Rio-Paris where the Pitot sensors got something wrong, leading to a disconnection of the autopilot, and the pilots did everything they could to crash the plane by themselves, while it was fully operational.