It's bad enough when you deal with third-party pop-up ads, but it's that much worse when the site itself shows pop-ups. Do you really want to subscribe to that newsletter before you've even read a single word on the page? Google wants to put a stop to this. As of January 10th, 2017, its mobile search results will downplay sites with "intrusive" interstitials and pop-ups. It'll accept content that asks for necessary info or takes up a "reasonable" amount of space (such as the app install banners in Android or iOS), but "click to continue" pop-ups and first-party sales pitches won't curry Google's favor.