Replying to @scottmichaud and @adambroach, @garjoh_canuck, @rochemathieu, @johnwilander
A browser works first and foremost for its users, that's documented as the Priority of Constituencies. If Microsoft had reason to believe that its users favoured DNT by default it is their responsibility to act on that.
The whole point of having a DNT API was meant to be that the browser could have a default but the website could ask for exemptions from that default, no matter what it is.