Back in the late '70s-early '80s when I spent my spring and summer weekends driving from Minneapolis to my parent's cabin in NW IA (and back again), I got into the habit of driving in the left lane, simply because as someone obeying the 55 MPH limit I was posing as a hazard to everyone else. (Meaning, everyone else was speeding, so being in the left lane let them speed without having to pass me.) Only rarely did I have to get in the right lane to let someone past me without their passing on the right.