Or do they simply don't measure the results independently?
My observation has been that for many, it's both "don't" and "can't."
Facebook makes it easy for people to advertise. Auditing your Facebook buy is a different skill set that requires different thinking, and more time than most small business owners have. So they just trust Facebook isn't lying to them, the way that they trust the metrics that the local radio station salesman gives them. Except that the radio station salesman will lose his job if the numbers aren't right. There is no punishment for Facebook lying to its advertisers.
My observation has been that for many, it's both "don't" and "can't."
Facebook makes it easy for people to advertise. Auditing your Facebook buy is a different skill set that requires different thinking, and more time than most small business owners have. So they just trust Facebook isn't lying to them, the way that they trust the metrics that the local radio station salesman gives them. Except that the radio station salesman will lose his job if the numbers aren't right. There is no punishment for Facebook lying to its advertisers.