I always thought it was a stupid idea to try and ask companies not to track you, instead of, you know, blocking trackers without telling them.

It really does seem like the advertising equivalent of BP's "carbon footprint", because the company doesn't like the alternative. In this case the alternative is blocking all ads and trackers for maximum user privacy. The commercial interests of modern web services and advertising services don't align with the values of privacy conscious users. So instead of pushing for things to try and make the advertisers feel more comfortable, make the users feel comfortable and encourage them to block that crap, and poison their fingerprinting data. These things benefit user privacy so much more than asking not to be tracked politely, and advertisers don't like them because they can't just choose not to listen or track the amount of users who don't want to be tracked.

Makes sense. It was an idealistic idea that was never going to work because it would rely on advertisers honoring a consumer’s request.

Unfortunate, but understandable :(
I wish we could rely on good faith with something like this, but it seems the only way is to block as much tracking as possible by force.

Without the force of law, this was never going to work.

Perhaps if the EU had used the presence of absence of the Do Not Track header as their method of determining cookie consent, it could have ended up being useful both from a privacy standpoint and to have saved us from the scourge of annoying as fuck cookie banners they ended up causing. Ah well.

Can't wait for the FUD posts about how Mozilla is the worst organization ever for removing this.

While the feature itself was not so useful, I do worry slightly about what the motivation for its removal might've been. People suggest that it's to avoid literally 1 bit of fingerprint data but the lack of more significant action on that front seems to contradict that idea. I didn't find any discussion of it in bugzilla, which used to be where you'd go to find out what the hell they're thinking.

Did they think nobody would notice? Are they going back to the bad old habit of removing features just for the sake of removing features? Did the fact that so many of their users have that flag set interfere with their ad tracking ambitions?

That is disappointing