What makes you think that they don't know?
As much as the elites here bemoan the state of diver training, from the insurance company point of view, it is still a viable business to write those policies. How many accidents are there that involve students and become insurance payouts?
I think the game changer would be lawsuits arising after incidents to certified divers, diving outside of a class. If those suits named the certified diver's instructor, shop, and agency, then the number of annual lawsuits-- and payments-- would be much higher.
As you can probably tell, I am not a lawyer, dive instructor, or insurance salesperson. Maybe these lawsuits do happen, but they don't get discussed here.