I'm not so sure. Here's Steve Jobs' 10 minute keynote address when introducing iAd, so we know exactly what he said about why advertising should be directly built-in to iOS:
"We have 185,000 apps on the App Store, created by tremendous developers. A lot of those apps are free, and a lo... the rest of them are really reasonably priced. We've got apps for free, for 99c, for $1.99, and we like that! Users like that! But these developers have to find a way to make some money. And we'd like to help them. Now, what some of the developers are starting to do is to put advertising into their apps. And, for lack of a more elegant way to say it, we think most of this mobile advertising really sucks. We thought we might be able to make some contributions. So that's what this is all about, it's all about helping our developers make some money through advertising so they can keep their free apps free."
... "The average iPhone user spends a little over 30 minutes every day using apps. Over 30 minutes every day, using apps on their phone. Now, if we said we want to put an ad up every 3 minutes, that would be 10 ads per device per day. 10 ads within 30 minutes, it's about the same as a television show. We're going to soon have 100,000,000 devices. That's 1 Billion ad opportunities per day in the iPhone community!"
Yes. But there's a bit of a difference. Ads weren't barred from iOS apps. iAd was a way for Apple to jump in on the ad revenue that was already happening inside those apps. Now they're putting ads in their own products, which is a different kind of behavior.
https://www.youtube.com/watch?v=q7WVt63S49s
"We have 185,000 apps on the App Store, created by tremendous developers. A lot of those apps are free, and a lo... the rest of them are really reasonably priced. We've got apps for free, for 99c, for $1.99, and we like that! Users like that! But these developers have to find a way to make some money. And we'd like to help them. Now, what some of the developers are starting to do is to put advertising into their apps. And, for lack of a more elegant way to say it, we think most of this mobile advertising really sucks. We thought we might be able to make some contributions. So that's what this is all about, it's all about helping our developers make some money through advertising so they can keep their free apps free."
... "The average iPhone user spends a little over 30 minutes every day using apps. Over 30 minutes every day, using apps on their phone. Now, if we said we want to put an ad up every 3 minutes, that would be 10 ads per device per day. 10 ads within 30 minutes, it's about the same as a television show. We're going to soon have 100,000,000 devices. That's 1 Billion ad opportunities per day in the iPhone community!"