This is literally the reason why I use ad block. I don't mind ads, but I can't stand webpages where the ad drops in an changes the whole layout. Congrats, you win 0 revenue from me!
Ditto - especially when I'm halfway through the first paragraph of an article and it slides it down offscreen, so I scroll down to keep reading, then the ad goes away and the place I was reading goes back up off screen. It's criminal.
Further, on my phone especially, I like to read articles while on the train. My trip has cell signal at every stop along the way, but not between stations. Before Apple allowed adblockers in Safari, I'd have about a 1/10 chance of actually getting the article to load before I lost signal. Now, it works great just about every time.