It's a fast narrowing funnel. Lots of advertisers try it. It works well for very few. The few campaigns that work well scale massively. That's why ads are so re

It's a fast narrowing funnel. Lots of advertisers try it. It works well for very few. The few campaigns that work well scale massively. That's why ads are so repetitive for users. "Advertiser" is also an overstatement as this article explains. Most are doing as arbitrage.