They are buying pop ups so the user doesn't need to click anything. The ads on the publisher's side are sold on a CPM basis so they don't need to click there ei

They are buying pop ups so the user doesn't need to click anything. The ads on the publisher's side are sold on a CPM basis so they don't need to click there either. The math just isn't going to work if you need to buy clicks on one side and sell them on the other. The big magic was basically video ads on the ad exchange. The advertisers paid more and had no actionable metrics to track, much less tracking clicks. There is some smart pricing, so the CPMs do get driven down, but not to 0. The hard part to this is what happens when you don't get paid or worse you get a bill going back months for money already paid out.