Because that’s a stupid system. I will never accept being under camera surveillance constantly by the car, no matter what stupid name people come up for it (“attention monitoring”)
I saw a similar reaction to Volvo's announced plans for such tech (it was a YouTube video) - it seemed to be a completely offline system, but people still read "camera" and reacted that they don't want "someone watching them" in the car.
But there's no such system, nor is there any trivial way of demonstrating that such a system works that way. Because all car companies and insurance companies want data.