alt Hacker NewsGoes to show the middlemen (the ad engines, ad auction sites) don't really have either the user or the advertiser's best interests in their mind. They just want to fill up the slots, and some ad agency is churning out ads and all they care about is some CTR/CPC metrics to get their fees, and the end manufacturer adds that markup to the product and charges them to the actual legitimate customers of those products.
Nail / head I think; if advertising was truly optimized for what a potential customer is interested in and might buy, there would barely be any ads.
But that's the "buy this now" type of ads, another big category that I don't see on the internet much (...because I have an ad blocker but that aside) is the "brand recognition" type - Nike and Coca Cola for example, a lot of their ads are passive in that they just want you to see the logo and become familiar and comfortable with it. Product placement in media.