The largest brands (Walmart, McDonald's, Coca-Cola, etc.) put a lot of analytics into their ad spend. I worked on an ad platform with a large audience that these kinds of brands wanted to get their name in front of, but the audience was exceedingly unlikely to click on big-brand ads on our platform. The brands figured this out quickly and pushed hard for cost-per-click rather than cost-per-impression because cost-per-click was essentially free brand marketing for them, even if they were paying $100 per click.

The next tier down was kind of the opposite. They weren't big enough to surface things like this, and they hired agencies for most of their ad spend. When focusing on the top of the funnel, there's this strange incentive with agencies where they often get more budget to spend if they can connect that directly to eye balls. Agencies are incentivized to throw the ads up everywhere and pay well to do so. They love cost-per-impression because we could deliver a large, predictable number of eye balls in a hurry.

All that said, we put no effort into getting around ad blockers as we were serving these ads on our own site/app and we viewed fighting ad blockers as fighting our users. Our ads were served inline in HTML, but clearly identified in the HTML of the page. It took blockers a while to catch on and block them, but they eventually did.