I saw this on the farm team...over half of the runners would DNF. You see they run the pace they want to run and when they know they can't hold it they drop out. They are afraid to run a "bad" race. Personally quitting is much worse in my book. I often see runners drop out to save face. In my opinion if you drop out the race it is because you know you will be beat. But I guess it is easier on the ego because they think they coulda, woulda, shoulda...