Pretty off-topic, but the reason why it isn't done is tracking, not ease of use.
Ad-networks want the ads pulled from their servers so they can track views. If web-owners serve the ads themselves, then the ad-network must trust whatever the web owner says about the numbers of visits/clicks/etc.
For now the ad-networks just don't care about ad blockers, because they are making money hand over fist anyway. If things ever get hairy for them, I suspect they'll switch to a reverse-proxy model. You point your domain to their servers as you do with cloudflare, and they they serve your content with ads injected in the right places, served under the same domain. This would be pretty easy for web-owners and completely nullify ad-blockers in their current incarnation.
Ad-networks want the ads pulled from their servers so they can track views. If web-owners serve the ads themselves, then the ad-network must trust whatever the web owner says about the numbers of visits/clicks/etc.
For now the ad-networks just don't care about ad blockers, because they are making money hand over fist anyway. If things ever get hairy for them, I suspect they'll switch to a reverse-proxy model. You point your domain to their servers as you do with cloudflare, and they they serve your content with ads injected in the right places, served under the same domain. This would be pretty easy for web-owners and completely nullify ad-blockers in their current incarnation.