"A passenger rode in my car, with the seat belt on. We had an accident, the anchor failed and the passenger was injured and today we are in court as a defendant ,the passenger is seeking compensation for their injuries.. here's how it goes.."
So, your position is that seatbelts are a liability due to possible litigation stemming from less than likely collision situations. That reminds me of a city attorney I once challenged who had the position that the city should give up many of its services because they could expose the organization to lawsuits.
When I installed the seat belts in my '31 roadster I noted how thin the sheet metal was behind the seat, so I added angle iron to spread the load over a larger area. An unlikely collision of enough magnitude to cause the belt anchors to fail would no-doubt be of such severity that passenger survival would be unlikely in any case. I didn't install belts in the rumble seat area as I don't plan on carrying passengers there, but if people were to use that seat, I would install belts, as the probability of real-world safety enhancement for the vast majority of more common collision scenarios, or other kinds of errant forces acting upon the car, is absolutely undeniable.