Wasn't this the business model of Google AdWords?
> Stop loading data from third-party websites. This is a security and privacy issue. There’s no technical reason why all ads can’t be served from the site I’m visiting. It can still communicate with ad servers, just do it on the backend.
Ad networks insist on this because there's no other way to prevent massive-scale fraud by the customers - how should the ad network know that the end user is a "real" user and not a fake request the customer generated to drive up the impressions on pay-per-impression ads?