So now we know a major reason iAds are going away. It's too bad, because the ad designs were rather elegant and usually fit the overall look of the apps from which they were served. Google's AdMob ad designs, on the other hand, are mostly tacky.
A bit of a spin or reach there. There are several reasons iAds were not successful. The biggest reasons aren't because of privacy security. iAds started at way too high a premium for buy in and it was riddled (at least at first) by such a production/approval process through Apple that no campaign could have been launched in a timely manner. Apple's control/tight reigned approach soured agencies who found it simply not worth it. That's why Apple started lowering the cost of entry and easing up on restrictions/creation process. But by then, it was too late.