I remember some time ago a report that said it was better to let the humans fly the aircraft with the automatics watching to warn of errors than it was to let the automatics fly the aircraft with the humans watching.
Humans make mistakes and become complacent - how many know they've read something and seen what they expect to see, not what's really there? If your automatics generally work fine and only report errors on sensor failure, how many people are going to immediately believe there's a problem the one time it really is a serious error?