For anyone who knows search better: did Google decide to not use click data because it was hard to get good rankings, or did they not use it because it’s hard to monetize ads based on click data vs other metrics?
Google's main product, AdWords, directly monetizes click data by charging advertiser's per click. No click, no payment. Can't get much more direct than that.
As little as 3 clicks seems to be able to bring an obscure page much further up the rankings for an obscure query.