How does the whole privacy minded ethos and ads work together?
Only because there is no physical way to do it, yet. If there was, do you think it would not be used?
On the web though, economic incentives and the availability of technology almost always mean that over a long enough period of time ad-supported business models will resort to available options to increase the revenue. Compare first 10 years of Google to next 10 years.
I hope that Apple, being a premium hardware and software vendor, will not. Their marketing team is working hard to drive the "Apple cares about your privacy" message, and so far that seems to be the case. They'd loose a lot of goodwill if they will start aggresively tracking their users and shove intrusive ads down their throats.