Some SEO text about benefits PPC advertising.

Pay-per-click, along with cost per impression and cost per order, are used to assess the cost effectiveness and profitability of internet marketing. Pay-per-click has an advantage over cost per impression in that it tells us something about how effective the advertising was.

Clicks are a way to measure attention and interest. If the main purpose of an ad is to generate a click, or more specifically drive traffic to a destination, then pay-per-click is the preferred metric.