"Advertisers don't know who you are" - You are wrong. Of course, they do know. Yes, they do not know the name but they know who you are based on your activity. Advertisers do not necessarily need to know your name to target a specific person or group of people. I may not remember your name next time I visit steemit, but I may remember "Sites selling your data" which is enough for me to know you on Steemit if needed.