Apple used to be friends with Google and used its search engine by default. That's not the case anymore—now Apple is "friends" with Microsoft and uses Bing. Both of those search engines like to track your every move - which is why you get those “tailored” ads. If you're into some extra privacy, try the latest option for search in the Safari browser: DuckDuckGo, "the search engine that doesn't track you." Go to Settings > Safari > Search Engine and toggle the browser you prefer.