Major advertisers starting following the DNT standard.
Then browser vendors broke the protocol, in such a way that it became useless.
We need ALL advertisers to be beholden to follow a DNT standard, not just a few key players.
Otherwise you'll just end up with all the other advertisers suddenly getting bigger when companies flock to the ad agencies that have better access to consumers since they are not honoring DNT. This will likely be followed by the ones that did agree to honor DNT ducking out of the agreement, because there are so many companies not following the rules so the initiative is worthless they'll say. The whole thing will just collapse on itself.