Non-rev passengers get to fly only when there are empty seats. Should there be a shortage of meals, non-rev passengers go without. They take nothing from the full paying passenger. And, at least at my airline, a non-rev will be in serious trouble should they detract in any way from a paying passenger's flight experience. I have lost count of the times that I have assisted regular passengers while non-revving and other non-revs have done more than I. I have transported lost bags miles out of my way so that regular passengers could get to their homes with children rather than waiting at the airport. I have sat and calmed passengers that have had mental breakdowns and panic attacks which prevented an unscheduled landing. Most non-revs are there to help when necessary.I have seen a non-rev mechanic leave his vacationing family, take off his tie and roll up his sleeves and dive into an aircraft engine where no maintenance was available thus preventing a delay or cancellation. So don't begrudge the non-rev too much.