You're completely right, and I think this gets to the root of what DNT proves -- that it was self-regulation under the assumption that it would not hurt advertisers or force them to change their processes for most people.

One can imagine an (admittedly unrealistic) alternate universe where DNT was off by default, but some kind of significant event caused a huge percentage of users to voluntarily turn it on. In that world, advertisers would probably still stop honoring the header. Because what they were implicitly agreeing to was, "we will stop tracking a tiny minority of users who might otherwise just block us anyway."

And to be fair, you can't really blame the advertising industry for not being on board with self-regulation that would force it to radically change its approach to business. I think that's why DNT still matters for illustrative purposes. It shows why consumer adblocking and anti-tracking tools need to exist outside of the control of the advertising industry. It can't be a partnership, because it's unrealistic and, frankly, unreasonable for users to ask advertisers to voluntarily kill their own businesses.

No tool that has an actual real impact on privacy to anyone other than a tiny percentage of already irrelevant users is ever going to come out of the advertising industry being "responsible". Any kind of voluntary standard that advertisers are respecting (using easily blocked cookies, creating well-labeled ads, etc...) only exists because most consumers aren't using it to protect their privacy or because advertisers don't have the legal power to get rid of it.

This is why my country was one of the last in Europe to abolish slavery. The government had to find money to compensate the industry. A sound argument on paper but considered an embarrassment now.

I just don't think it's fair to ask advertisers to voluntarily help me with that.