Is it not common knowledge that clickthrough rates for online ads are execrable? I recall a discussion here a bit ago about ad tracking and it seemed like a lot of commenters thought that knowing how well an ad worked was as easy as taking the tracking ID of the click that brought the buyer to the seller's site and looking up which ad it was and where it ran.

But clickthrough rates are so bad that they are effectively useless for even for so-called useful ads that nobody with any sophistication cares about that metric. Pretty much the only thing that adtech talks about is CPI now.