Problems with prerendering ads: 1. Prerendered ads would still be detectable if you leave in your tracking code client side. 2. If you take out the tracking c

Problems with prerendering ads: 1. Prerendered ads would still be detectable if you leave in your tracking code client side. 2. If you take out the tracking code, then it would have to be handled on the server side. Which leads to the question, whose servers are handling this? And how is the data aggregated? 3. Also, without tracking code client side, it would be far less beneficial to advertisers because it would be much harder to tell who you are when you visit and decide what ad to serve you. I'm sure there are ways around this, but it is far more difficult compared to what they do now. 4. Caching. Of course these problems aren't impossible to get around, but prior to the iOS 9 stuff, there really was no benefit to even consider doing any of this.