From a selfish POV isn't it better as an adblock user that other users don't use adblock? Then they unwittingly subsidize your pleasant ad free experience.
As more people switched to contextual ads, the ecosystem for it would also improve and rates would hopefully increase (for smaller sites).
With non-surveliance based ads, they can make the ads completely indistinguishable from normal content in their CMS and make it look like first party content and server side based. And since the user info will be minimal beyond an IP, it will mostly be content based vs. user based. They can even do things like podcasts & youtubes videos do with sponsorships that come with the content.
They don't do it because it doesn't make as much money as the current status quo and would require more work to integrate if it was offered.