It's not about having low intelligence. It's about being caught off guard. Not everyone is in a big city and have constant contact with fraudsters. Some people are in small towns where they trust everyone and when they receive a call from the supermarket or some other place they usually just trust them too. So, they are not attempting to find all the flaws in their reasoning, they may just think that the wording was a bit off, but an understandable mistake and continue the conversation.
