Google's business model is to help Google's customers pay money to Google. Google Search's customers are mostly scammers who run adverts. Helping the user find a thing is at odds with helping the user find a scam that pays Google money.

This is somewhat true; despite what HNers seem to think, online ads are not very effective (in terms of convincing people to buy things), and Google 'screws over' its advertising customers as often as it delivers deficient search results to users.