Hey, I work in advertising, I can provide a little insight here. When we want to advertise to a specific type of person, Google (and other social media compaines) doesn't give us data and let us target individuals. What we do is select certain keywords, phrases, or interests that we want to target, and their algorithm uses your data to determine if you're the kind of person that we are trying to advertise to. Detailed data is important for Google, because if their data is bad, our ads won't go to the right people, and we won't make sales, so we'll spend our money elsewhere.

Tl;dr advertising revenue is data revenue.