For starters I don't drive a multi-ton death machine unless your multiplier is less than 2.
I would contend that it is not possible to drive for any length of time and still have 100% of your focus on the road. Even if it were, I would further contend that the vast majority of people who are on the roads are not doing so. The relative safety of the roads would appear to contradict your statement.
I also ride motorbikes, and agree that compared with a car you are hyper-aware. Probably because you feel like you are in the environment rather than in a metal box, but even then once you start riding any distance you start thinking about the beer at the end of the journey, or the shopping you need to do, or feeding the cat or whatever.