> but they are in fact the largest aggregators of data which feeds into the system.
Feeds into what "system".
Do you really think Google/Amazon/Apple/etc are handing over your Name+Phone number to say Spokeo [1]? I just don't think you get it. Your phone company is the one that is selling your data to anybody not FAANG.
It's easy to say some "ad-tech" are doing X, but actually get a whiteboard out and start with say Google and list what products of theirs collect what data. Then list the process by which say the USG buys its from Google. I'm very interested in what names for the processes are going to be because I really doubt you'll find any for the ad-platforms.