Gullible and greedy has a lot to do with it
A friend has paid many times for delivery of various "free" gifts, from various organizations, 2 that come to mind are a "UN rebate from the US IRS" and a so called "Samsung anniversary draw".
There have been many others including 1 in which apparently he won 4,000,000 USD (to be delivered in cash along with a Bently Continental and numerous other prizes), during the process of paying for delivery, re-delivery, repairs to a broken down vehicle, accommodation for the delivery personnel, he received a phone call from a supposedly Senior Thai Police Officer threatening him with jail if he didn't pay the next instalment.
Another time was the imminent arrival of the FBI to arrest him for failure to pay the delivery charges.
He has also been threatened with the removal of his name from the pension roll.
To this day he has paid out much, received nothing except more requests for money and more threats and doesn't listen to advice, he wants to ensure his son has money after he dies is his justification for doing it.
Simple approach "if it sounds too good to be true then it probably isn't".