It seems particularly bad lately. The pattern I've noticed is:

* A totally pointless introduction paragraph, devoid of info.

* Big ad

* A sort of teaser sentence in large font so that it appears to be the length of a paragraph. High noise to information ratio.

* Larger ad that loads as you scroll, so you're more likely to accidentally hit it

* Another sentence with high noise to info ratio.

* Repeat.

I think one of the SEO perks of this pattern is how it takes forever to find the information that you know must be somewhere on the website, so users seem more "engaged" because they are scrolling and spending more time visiting the site.