Another blow to privacy. I really hope Apple would come to search market and challenge Google.
Search does not require advertising.
Advertising is probably the simplest way to monetize search. Certainly other strategies could be tried, but that one at least is well understood, and nigh-ubiquitous.
It could also just be sold as a service, or an addition to iCloud+.
If there is an opportunity to increase revenue (subject to mission/values/etc), you take it. A decrease in another line of business doesn’t matter. Or an increase; you wouldn’t say “hey we’ve got this amazing ad opportunity but the AirPods business is killing it so let’s not bother.”
I guess the nuance here is that the business decision might be “our search, with our ads” versus “Google’s search, with their ads, plus $15B/year”. In that case I think there’s a reasonable argument that users are better off with Apple’s ads than Google’s.
If someone searches for "hotels new york" you have what's called a motivated customer. He or she is much more likely to click on an ad for New York hotels.
It's one weird trick, but man, is it a good trick.