In my view it's mostly about justification.
What's your age, sex, and race? These are questions that, in and of themselves, are not private. Any stranger on the street who sees you could immediately answer them. And if you've ever posted a picture on the net, you can add far more people. And you probably wouldn't be bothered if every single person in the world knew the answer to this question. And in fact you've probably told everybody the answer to these questions, even if indirectly, in your own posts.
Yet in spite of all of this, you probably would not want to tell me. And that's largely because I have absolutely no justification in asking or knowing this. If I said I was surveying developers, and you believed me, then you'd probably be more than willing to submit this information to me however.
Google wants to harvest massive amounts of information on me to, at best, try to get me to purchase things I otherwise would have no desire to purchase. And that is, again, at best. This is the same company that literally black-listed the term "human rights" for their proposed engine in China. [1] To imagine they won't, if they are not already, use that information for even more nefarious ends is being naive.
So on this front I couldn't care less if every disinterested person in the world knows what I had for breakfast (it was muesli), yet I would not want Google to have this information, because I don't think they are justified in knowing it. More sensitive information just ends up reaching a higher and higher standard of required minimal justification.
[1] - https://theintercept.com/2018/12/01/google-china-censorship-...