Earlier quoted context omitted.
Because the fully-assisted driving ("autopilot") removes the need for interaction completely. Your brain will stop spending power on backseat driving, because the brain is really lazy--and clever about being lazy too.
>Because the fully-assisted driving ("autopilot") removes the need for interaction completely. But it isn't fully assisted and doesn't completely remove the need for interaction. It just is another step forward from cruise control that is more assisted and requires less interaction. I am not sure why everyone assumes the sweet spot for driver assistance ends immediately after adaptive cruise control and before cruise…
Your characterization of autopilot as “just cruise control” is fundamentally incorrect. Mere cruise control still demands significant and continuous attention and manual control on your behalf (steering). Autosteer makes the leap to fully automatic, which opens the door to not paying attention for long stretches of time.