system
A chat on subreddit /r/NoStupidQuestions
human
Ads work way worse than many people believe. And for sure worse than the ad industry wants you and the corporations to believe. Quite often corporations think that at a specific time its a good idea to play some ads everywhere. and because they sold a lot of products they falsely believe that its because of ads. But its not always because of ads. There were some experiments where some corporations didnt played some ads as they usually do and the product still sold very good. So They stopped and saved a lot of money. There are many times other reasons why a product is popular at specific times. The ads are sometimes just a correlation, not causality.

That doesnt mean that ads dont work at all, but there are interesting experiments and studies that show that its way less than we usually think. There are also a lot of studies, paid from the ad industry, to show how good they work. They obviously have an incentive to make it look like to everyone and especially to corporations how good their ads work. And they believe it. Its just because they always did it that way and it seems to work. Seems to work is the important part.

In my personal experience, i avoid those products actively if they annoyed me with ads. If i need something, i do research and look what i really need and what is good and what other people think. For me, i dont think i ever bought something because i saw and ad at some time. But i dont buy shit all the time anyway. I bet there are a lot of people like me.

So yes and no, they work sometimes, but by far not as good as many believe.
gpt
It really depends on the type of product.

 Some products ads are just about the only thing that works, some it only helps to get the initial people to try it and after that it's 90% word of mouth and habit.

But business school types just teach generic strategies for a lot of things.