Interesting statistics, thank you.
I think it is texting / other distractions available in cars. For example, I used to have two knobs and five buttons on my radio. Now I have two knobs and 21 buttons! My climate control has two knobs and 12 buttons. That was three sliders. Bottom line, changing anything takes more thought.
Also, cars are bigger and quieter, with less sensation of speed. In my first car, going 80 was a hair-raising experience. Now 80 can be driven under total control - but physics don't change; the kinetic energy of driving at 80 is still 80% more than driving at 60.
Not sure what the solution is - noisier cars, less functionality, or automate everything to take the human element out of it? (I know there are valid arguments against the latter.)
I think an easier part of a solution is to add logic to cell phones: GPS and map information is built in and could be used to time interruptions. For example, if the car is approaching an intersection, delay delivery of a text message.