As far as I'm concerned, it is just great that something made it for people to be "all up in arms about it". And "why" is not very important and neither is it surprising, really. I mean, how could have people been all up in arms about well-established technology all web is built upon, when 10 years ago google was, allegedly, "the good corporation", all people were like "I have nothing to hide", avoiding FB because of privacy concerns was just "being paranoid" and people telling stories confirmed by Snowden shortly after were "schizophrenic"? It is literally like 3-5 years (right before Cambridge Analytica scandal, I guess) since being "concerned" about your web-presence became somewhat mainstream.

And FLoC is... well, it's new.