As I said, it's not the cost issue. It's the whole legal process.
These kind of cases can go on for years and eat not just money, but time, attention and energy. And your insurance is most likely only going to pay out once the case is complete. Where do you find the energy and money to fight it?
Another small company I know recently closed their doors in a relevant situation. They installed a big automation system. (Their first big one and their 'big break'). But it did not perform to the vendor's specification (according to the client) and they removed it. Financially it killed the company.
I was actually asked to arbitrate and was happy the system did perform. But the client was a lawyer and he threatened to keep them so wrapped up in legal proceedings that they buckled and took it out. The vendor (quite rightly) said the system did perform and did not take it back.
So small company suddenly sat with a few R100K worth of second-hand stock. They eventually closed down with a big second bond on their home.
So, it's easy to say one should pay the insurance. But that's only the tip of the iceberg. Those who own small companies doing big projects will understand.