Earlier quoted context omitted.
It’s a bit of both. It’s not possible to rely on browser controls as-is, because they do not differentiate between necessary and optional cookies. Browser vendors could agree standards and implement them, exposing these to users and advertisers in a friendly way. But they haven’t shown any interest in doing this. I wonder why?
Without laws forcing companies to properly declare which cookies are "necessary", this control you imagine does nothing, as every company simply sets their advertising cookies as "necessary" One of the hundreds of reasons do_not_track failed. You cannot do something that trusts the website operators, because they are egregiously untrustworthy. The cookie banner everyone keeps bitching about is a direct example of thi…
My point is about UX: it could be much slicker if the browser industry standardised the consent mechanism.
You make a good point about lack of incentives.