I don't remember the exact timeline but MS decision to enable DNT header by default was basically a poison pill for the entire concept before it had a chance. It would have failed one way or another though. Adtech industry doesn't give up that easily.
That's the argument I've heard from the ad industry, but I don't really buy it. Previously, the DNT header was missing by default, so it's presence could be seen as user intent to forbid tracked, while its absence is ambiguous. Afterwards, the DNT header was present by default, so its absence could be seen as user intent to allow tracking, while its presence is ambiguous. That's exactly what should be the case should be, where only explicit consent to be tracked counts.
Safari/Chrome/Firefox enable by default some ad-blocking today, just like they disable popups or screen for phishing sites.
The whole "users didn't opt in" thing was a false narrative manufactured by the ad industry. You don't need to ask a customer to disable bad behaviors without asking.
