The difference is in the sheer amount of training pilots have to go through, and the regulations that they, and their employers, are required to follow. This is tremendously different from a car that throws up a couple of warnings that can be quickly and passively acknowledged prior to your using "autopilot".
You can't passively acknowledge it. It requires actively agreeing that you understand prior to use. The dialog in one version makes reference to autopilot in the pilot definition.
Maybe when this accident happened it was different, but as far as I know it's always been behind a confirmation dialog.
To operate a motor vehicle in the US, you must be licensed. That surely holds some weight here.