My guess: because the limit to Google getting paid isn't inventory. There's effectively unlimited places on the internet to put ads. What is limited is the do

My guess: because the limit to Google getting paid isn't inventory. There's effectively unlimited places on the internet to put ads. What is limited is the dollars flowing in from advertisers. If they perceive Google Ads to be fraudulent, they bounce. Put another way: someone testing Google Ads with a $100 ad buy is (my guess) 1000x more valuable than a (new to Google) publisher someone showing $100 worth of ads. If the former experiences fraud, they leave. If the latter has their $ yanked by google, eh, there's still trillions of ad slots per day available.