Why didn't the moron have insurance?
This is mere speculation, but if he has enough money, and was still into the meth (it is established he used it at some point, right?) Then having insurance on the house in case of a lab explosion would be pointless...if there was a lab, regardless of the source of the fire, insurance policy would be voided anyway. Also, there is less chance of an investigation into the cause of a fire if there is no insurance company involved...hence the "undetermined" ruling. They just dont have any reason to check.