The main problem is that we are human being, that we are *NOT* robot.
As human beings we are the product of millions of years of evolution - an evolution that did not encounter _any_ form of electronic gadgets until very recently.
The fact that we can drive a car (or any vehicles) is not because we *adapt* to the way the car operate, but it is another way around.
We engineer the vehicles so that they can become our tool, and the operation of that tool is *within* our range of capability.
While using cellphone (and now smartphone) have been accused of causing a lot of accidents, they are not the only distraction. Long before the advent of the cellphone, a lot of traffic accidents were caused by drivers adjusting their radio (either looking for station of turning up/down the volume), or adjusting the seat, or the air condition, or whatever.
It is thus evidenced that we human beings are not made to be effective "multi-tasking" device
And smartphones are not the only culprit - I have known drivers who were so distracted by their on-board sat nav devices such as tomtom (and other brands) they drove their car into poles, walls, and so on
Personally when I drive, I drive. If I have to adjust my seat, my mirrors, my radio, or whatever, I stop my car at the roadside (or any other safe place) to make the adjustment, and then continue my journey.