We've even had P3P spec that allowed users to say in browser's settings "I don't want your tracking cookies", without any consent pop-ups. It was even implement

We've even had P3P spec that allowed users to say in browser's settings "I don't want your tracking cookies", without any consent pop-ups. It was even implemented in Internet Explorer! And then Google found a loophole in the P3P syntax, and abused it to bypass it entirely. Fun times.