How much weight is too much weight?

This subject reminds me of my first job out of college. I went to work for a contractor that did formwork and poured concrete. The first big job I was assigned to I ran the calcs on the formwork design that the superintendent was planning on using for the pour. According to my calculations, the forms should have failed in shear. When I brought it up to the owner and superintendent, I just got that kid out of school eye roll and the pour went on without a hitch like it had all the other years they'd been in business. Truck makers are worried about being sued. What safety factor do you imagine they really use or publish? IMO, it is why we see so many trucks with campers that based on the trucks specs should be flat as a pancake on the road.