Depending on where the damage is situated, you can determine/guess the cause. My 2003 has no dings on the side, but I almost never park at shopping malls - If I do, I try to park defensively ... Most road rash is on leading edges: hood, bottom of doors & rockers, and any part of the vehicle body that sticks out...
You can purchase some tapes to protect these areas, or paint them over with rocker guard/ truck bed coating etc ...
Longer mud flaps help reduce flying rocks and debris - keeping a greater distace when foolowing on dirt roads will help ...