This is a prevalent misconception that assumes advertisers don't care about how their money is spent! Advertisers and Google are actually concerned about SEO garbage. Nowadays, most advertisers tend to pay based on # of conversions, its value and ROI. Those spammy sites usually yield a garbage CVR even though their CTR seems great. Advertisers don't like this.

Looks like people don't acknowledge that # of clicks is no more important metric. That seemed to be important when it was the only meaningful performance metric. But the ultimate metric that matters to money is advertiser budget allocation. If they see Google search performs worse in terms of conversions, they will cut their budget there. And this is the real problem that Google has.