Some years ago I was involved in despatching some "hazardous" material (similar to superglue) all suitably packed in inert packaging, along with the main product onto a corporate jet which which had flown over from Nova Scotia specifically to collect the consignment. The company concerned took no chances of not having the right people on board, even to the point of having brought their own import/export agent with them. At the UK end, the lady at the information desk apologised to to the pilot for having to charge him an extra $30 for something or other. He just waved his agreement to pay what ever the cost was.
What the airport, (South Humberside as it was then called) didn't know that the lack of this product was costing the company around $30k per day! Hence the apparent lack of interest of the pilot in an extra $30 charge. So I suspect that many handling agents "try it on" as other pressures may be affecting decisions as they were on our flight.