Rear hitch boxes / carriers?

For those that say they see bikes on the roadway, parts falling off rigs.....how do you know they just weren't tied on right? We watched a John Deere tractor tumbling front over end headed right toward our MH one time. The guy had put it on a flatbed trailer.....NO tie-downs! He started up a short incline off an off-ramp.....and disaster (it was a new one!!!!!). So, I still stand by that if you attach items correctly, have stabilizing rods attached and attach to the frame, you can carry quite a bit on the cargo carrier.