I was looking at some of the new answers, but this caught my eye. My feeling about the builders insurance that is on offer is that it sorta falls into the home business or craft coverage where they are probably thinking someone might slip coming into the shop, or get grease on their suit. If we are talking about moral and businesslike, I wonder what the insurers would say if they really knew the skinny on what we thought they were covering. If they knew that there weren't any industry standards, or qualifications. If they knew most people were self taught. If they realized the kind of accidents that could happen in a catastrophic failure. If they realized the operating environment was unlimited (not just on road use). If they realized builders were making add hoc adjustments to frames, with no engineering. If they knew the whole specialty was built on archaic practices that were superseded by the manufacturers years ago. I'm just throwing that out, but there is a list that should scare them that could be worked up. If they really knew what they were insuring I doubt very much it would be a cost that builders could easily absorb.

Insurance is a contract, and few people ever read the policy. There is probably something in there to cover them if something unusual happens that is out of their comfort zone. I know I have run into that time and again. It turns out you are covered, just not for the thing in question. Like maybe not covered for anything that does not happen on the premises. You would be appalled how bald some of the exceptions are. Of course they may chose to pay in any case, so as not to rock the boat, if it's a few hundred dollars.