> they sell their ability to know everything about you to anyone willing to pay for that information
This does not actually claim they will sell you a copy of the raw data. That is Google’s “crown jewels” and they protect it fairly well, although not always perfectly.
In the past you could see the query on a referral URL. In the past you could see PII coming through this way as well. You could target ads against this PII, etc.
But anyway, what Google does is let you target ads based on their absolute knowledge of the user. What you are Searching for, where you are Searching for it, etc.
Google tracks you incensently so that they can more effectively sell things to you, or sell others the ability to sell things to you.
But increasingly it seems that Google tracks its users just because it can. Just in case that clickstream or that app history or that voice recording might become useful someday. Google tracks you like a paranoid government might track its citizens, afraid that some scrap of data might come back one day to be useful in its almighty question for [control / dollars / training an AI / optimization / whatever].
The nominal cost of storing one more piece of metadata is zero, the potential future value seemingly limitless, and perhaps the fear of Management asking for some piece of data you didn’t think to record is so great, they seem to just record all the things.
