They could just as easily show ads in answers, the advertisers wouldn’t care. In fact, I can see how a major advertiser would rather prefer that an ad is shown in Google’s own trusted UI rather than on some random website next to who knows what sort of content (that motivation is behind YouTube’s “demonetization”).

I was referring to google‘s one ui but I agree with you. I am wondering if all the going back and forth by not finding what you are looking for increased the ad numbers (even if short term).