The do-not-track header is just another bit for fingerprinting you, I don't believe any ad-company actually honors it. Also, why trust that they do, when there's a solution that doesn't need trust?
I want the browser to not let any other party get more bits of entropy than I agree to. My ip is a few bits of entropy. Now I want my browser to give not-that-many-more bits of entropy to any remote server. If it allows a remote server to list my system fonts, render something on a canvas and read back the bytes,or do some audio mixing on my machine and read back low level results, then my browser has failed me. I want it to say "I'm not showing this webpage at all because it tried to read back a canvas".