Because people who really need the privacy can be identified. Ideally, you want to help them so that their browsing don’t stand out (so that their browsing and yours are virtually the same).
I mean, isn't the only way to go about that to be completely vanilla or do what the masses do, then? Because if you start blocking all these cookies, canvas, javascript, etc- won't your browser's fingerprint be even more unique since you'd be the only one who's traffic data would be incomplete?