I've come to the tentative conclusion that advertising is, in most cases, kind of like money spent on good luck charms. The company wants to spend money on convincing people to buy their product (or service or etc.). Telling them, "there is no good way to do that, you'll have to just make a better product", is never going to be believed. They want to think that they can just spend money, and get money back.

Improving your product also requires money, probably, but in addition it would require good planning, a realistic vision, organizational competence, and a lot of other things that are harder to deliver than just buying ads.

Executive buy ads because it's easy to do, compared to making a better product (or service or etc.). So your ad company doesn't have to deliver better sales, it just has to be at least as good as other people's ad services. Because most executives are not going to promote the guy who says, "there is no easy way to spend money to get higher sales, you're going to have to do it the hard way".