Another thing is regarding k-anonymity which I suppose privacy-first guys would use. If I gather user info with a high entropy, I don't have an incentive to sell it to anybody and create a competitor, and it'd probably illegal to do that. But if I anonymize the data set into a k-anon data it's now less restrictive to sell from legal point, also I'll probably sell that data to third parties just to make ends meet.
https://help.duckduckgo.com/duckduckgo-help-pages/company/ad...
> Weinberg: We make money the same way other search engines make money. When you type in “car,” you get a car ad. We syndicate Microsoft and Yahoo ads through the Microsoft Yahoo Search Alliance.
[1] https://www.forbes.com/sites/forbestreptalks/2016/02/19/the-...