And I don't like the notion of google offering free services, when they are a commercial company and not a charity.
And "helps making this more efficient" ... well, a tiny bit more. Knowledge is power.
Google posesses a lot of knowledge.
But even "only the ads". There are worlds between showing someone random ads, or a highly tailored custom one, made out of all the online and much offline activity of that person.
And knowing allmost all about what a company is doing and controlling their communication is potential valuable in various ways as well.