Non-contextual advertising still exists, but it's perceived as less effective, so there's a lot less money in it. I don't know if that perception is correct, but I do remember back when a common complaint from people was that the ads they saw weren't relevant to them.
It's also not just targeted advertising that will be affected. Without any sort of user tracking, it will be even harder to prevent fraud. No one wants to spend money showing ads to bots.
> Also I assume / hope that iOS ads aren't tracking people either; third-party cookies simply have no equivalent in the iOS app sandbox design.
You might want to look into the Apple Advertising Identifier.