Google doesn't charge for ads, it charges for impressions. If you user doesn't seem it, google doesn't get paid.
It also seems like a very different tech than trying to determine what an ad script will actually show a user. So it's not easy as if they can do A they can do B. Still doesn't excuse the fact that they should be doing their best to block those kind of ads in their ad network.
FWIW, "impression" means "request". Who knows what the user saw.
Google AdSense is pay-per-click (or some algorithm, based on clicks against and the subject matter's value). In the context of adware rubbish, we are probably talking about AdSense. So no, Google doesn't pay per impression.
DoubleClick (part of Google for some time) may still offer an impression-based product. My experience of them a few years ago was that they'd negotiate on anything if you have enough traffic to make it worth their time.
Are you talking about google paying the website for each click/impression or are you talking about advertisers paying google for each click/impression. Both are termed under impressions (CPM or PPM). And in both cases google loses money in rolling out this feature.
It also seems like a very different tech than trying to determine what an ad script will actually show a user. So it's not easy as if they can do A they can do B. Still doesn't excuse the fact that they should be doing their best to block those kind of ads in their ad network.