1. I scroll down, read the article a bit, move to scroll again, and end up clicking an ad that has just popped into existence (Cynical reason: The delay improves their CTR and hence revenue. Less cynical reason: They were too optimistic in how fast their ad would load on my mobile connection).
2. I click your page and it starts playing noise. It doesn't even have to be an ad, a lot of news sites autoplay their videos when I just care about the article.
Both are less about where the ad is and more about how it behaves
Another factor in #1 is advertisers don't want to pay for ad impressions if the ad was never actually viewed (because it's way down the page and the user never scrolled that far).
1. I scroll down, read the article a bit, move to scroll again, and end up clicking an ad that has just popped into existence (Cynical reason: The delay improves their CTR and hence revenue. Less cynical reason: They were too optimistic in how fast their ad would load on my mobile connection).
2. I click your page and it starts playing noise. It doesn't even have to be an ad, a lot of news sites autoplay their videos when I just care about the article.
Both are less about where the ad is and more about how it behaves