How do advertisements add value to society?

 How do advertisements add value to society?

There is no mandate that advertisements add any value at all - either to society or to the product; the expectation is that the entity which pays money to have this advertisement be done is doing its due diligence so not to look too stupid in public.
Well, there are many examples of where this went wrong: 
The adding/destruction of value for consumers is actually up to the consumers, and something which looked simply awesome during a presentation within a closed environment can go really bad with a larger audience.

Still, advertisers did not win a couple of battles when they went a bit too far with their pursuit of what they believe the consumers had wanted. Here's one of them: 
The ads are aimed at their target audience, and you would agree that humans, even within the same geographical location, are not a homogeneous mix: there are those who like to aspire to be/act/feel/have whatever it is depicted on the advertisement; there are those who are immune to the ads; there are those who are offended by ads; and there are those who like ads because they are in a business of creating them.

Thus, as a finance person, I would say that the only value added is the money spent on creating advertisements and keeping those advertisement agencies (and printing companies) employed.