Google paying for ad click only when sale is made

In response to the article "Quality Score Explained by a Former Googler" on SearchEngineLand.com, wouldn't it be interesting if #Google introduced a CPS, cost-per-sale. #Larry Page should consider this business model but of course won't because #AdWords has become Google's main revenue source and this would seriously reduce that revenue stream. As it is now, Google's job is done when an ad is clicked on, even if a person clicks on an ad only out of curiosity and has no intention of making a purchase. An ad is clicked, Google gets paid, and they're done. I noticed that quite a few of my monthly top-four-sites were in Mandarin, although what I was advertising was a novel written in English and I had selected English as the language for the ad campaign. If the carrot were held a little farther out, it would be in Google's best interests to ensure that impressions displayed on the most appropriate sites. I'm under the impression that the tracking technology already in place is sophisticated enough to allow Google to track a user's clicks from ad to landing page to check-out. Every advertiser would benefit from Google not being paid until an actual sale is made.