TV advertising is extraordinarily expensive.
It only yields a return on investment if you’re advertising something mainstream that is likely to appeal to a large proportion of viewers.
Although it’s called “Pro”, the appeal of the iPhone 17 Pro is as mainstream as it gets. Sure, it’s somewhat aspirational because it’s expensive, but almost everyone understands what you’re getting: long battery life, tele camera to “zoom in”, Apple’s best effort at chip performance, etc., etc.
TV advertising works well for that: most viewers could be tempted to buy a Pro if only they knew about it and could afford it.
The Air has a slightly different audience. It has a less-is-more aesthetic, comes in fashionable barely-there colours, and has symbolic value (status, taste, signifier of cultural capital) in addition to its practical value. It’s for people who think they’re smarter than the great unwashed and appreciate minimalism.
Huge swathes of TV viewers would not see the point of an iPhone Air, just as they don’t understand luxury products generally. Does Ferrari do TV ads? Taeur perfumes? Hermès? Omega? No. TV is for things that ‘everyone’ understands and might conceivably afford.
The Air will be advertised in a more targeted way in channels that make sense for luxury tech products.