The could use a cookie with no tracking id for the default storage. Granted, it would just be for the specific device but there's nothing technical stopping them from making that option available.
There's a micro-industry of journalists who teach users how to express their consent, even if vendors use a dark-pattern privacy UX. If less than 0.01% know to request a non-existent option, more may choose that option once it exists and they have been educated on the benefits. Witness the rise of ad-blocking and past industry attempts like "Do Not Track" and "Do Not Call".
Ad Blocking stops ads from being shoved in your face. There's an obvious and immediate benefit to every user who tries it.
Do Not Call stops annoying phone calls from interrupting you. Again, people demand it, because it makes a real difference in their lives.
Do Not Track, on the other hand, seems to be a total flop. (In FireFox, 8% adoption rate and falling; in other browsers, presumably even worse.) I don't see how you could refer to "the rise of Do Not Track" with a straight face. This is due in large part to the fact that the vast majority of people aren't particularly interested in making the ads they see less relevant and don't really care about whether a website is giving them an anonymous cookie.
There's a long history behind the collective implementation failure of "Do Not Track". The point is that there was stakeholder demand for the feature, even if the demand was to avoid regulation, or even if the implementation was botched.
Which stackholders? I've never seen demand for DNT by the advertisers, it was an initiative by two researchers working for Mozilla and the ACLU, and which was then taken on by the W3C. From what I can tell, the industry mostly ignored it.
"We first met to discuss Do Not Track over 2 years ago. We have now held 10 in-person meetings and 78 conference calls. We have exchanged 7,148 emails. And those boggling figures reflect just the official fora."
From what I can tell, an initiative by some consumer advocates (under the umbrella of the W3C) made enough noise and got a few people from some companies to join a mailing list and do a few conference calls. Most of the major ad companies (Quantcast, KISSMetrics, etc) didn't even join the group. Predictably, since the industry has no interest in advancing the issue, the group died without achieving anything.
