The primary purpose of ads isn't to get you to buy something. It's to plant a brand in your brain so that next time you do want to buy something, you'll think of the brand.
Ads are very good psychological manipulation.
Here's a thing that I am absolutely convinced happens. Ad network tracks purchases. Ad network track ad impressions. Ad network correlates the two and finds that 90% of people who saw the ad also bought the product. But they conveniently "forgot" to check if the ad impression was before or after the purchase.
I'm confident this is happening because the only times I see ads for anything I'd be interested in buying is after I've already bought the damn thing.
But do they at all take into account the fact that probably about 50 out of 100 ad impressions lead to an "I'll NEVER purchase anything from the purveyor of this ad-spam shit!" reaction?
Of course those are also really ads in a sense, but somehow there’s got to be a way to provide a real search engine that doesn’t show only e-commerce sites. I’ll pay for it!