I think you will find the culprit behind the vast majority of terrible drivers: THE CELL PHONE!
I don't care what most people say, you can not drive and talk at the same time. I was a passenger while my brother was driving when he got a call
from his wife. His driving was erratic, even while he "paid" attention. I told him that and he said "I can drive while talking, the others
can't"
I refuse to answer my phone when I drive.