Apple uses their data to make better product to sell to you. They don't sell their data to advertisers because they don't need to.
What is going to happen if iphones, ipads, etc don't sell as well?
The data that Maps collects while you use the app — like search terms, navigation routing, and traffic information — is associated with random identifiers so it can’t be tied to your Apple ID.
Or Apple Pay:
When you use Apple Pay we don’t track what you’re buying, so we can’t build a purchase history to serve you ads.
Or Siri:
If you give your explicit consent, Apple can improve Siri and other intelligent features by analyzing how you use iCloud and the data from your account. Analysis happens only after the data has gone through privacy-enhancing techniques so that it cannot be associated with you or your account
Note the word "can't" that appears over and over. Yes Apple necessarily records some data, e.g. for streaming services. But broadly speaking, Apple couldn't sell the data to advertisers even if they chose to, because they don't have the data.
Given their track record on privacy, particularly using it as a selling point, they'd be poisoning the well pretty badly if they did this. It's more likely they'd burn through their cash before even thinking of selling user data.
I can't see it happening on Tim Cook's watch or any of the existing executive team, but maybe an external hire.