it's an ad industry thing, not a site thing. The ad industry would really have to build the solution to host on the sites, and the problem then becomes making something every site can reasonably host, and all the headaches associated with that.

And I have the suspicion that doing it wouldn't add much to the bottom line of the company who invested in it, despite how much they like to complain about ad-blockers.

That makes ad fraud detection much harder, which is something the ad industry is even less willing to accept than ad blocking.