Advertising was created some 100 years ago and it works very simply. The more you tell people about your product, the more likely they are to buy it.
Back in the 1930s this was a great concept as you have nowhere to go to get information. Now, you have the internet and can go on-line and research products and services.
One of the reactions we have gained from this tsunami of data hitting us, is we tune out. We are bombarded with adverts and sales messages every day and we just tune it out. "We are number one" everybody says that, "we are the biggest" everybody says that ... we are bombarded with corporate messages everyday. The same with adverts nobody reads or listens to adverts.
You know yourself you fast forward through as on the TV, switch radio channels when ads on on the radio, scroll through ads on Facebook.
I've helped a number of students with dissertations in the past and they all ask me when they are being taught how to use ads when they are a irrelevant. The only people who believe that ads work are people that sell them.
Think of it this way – if you were to build a massive billboard in a city centre, you might have thousands of people seeing it each day. But how many are interested? Facebook knows what its users are interested in, so it can make sure your advertisement appears in from of people who have shown an interest related to your product or service.