Most of the Websites today have adopted a mobile-friendly layout design and many have their own Apps for mobile. Google will soon down-rank sites that greets an organic user with a full page App install ads / banners.
User experience is one of the key ranking factors in Google Search Engine. When a user visiting a site via search engine is greeted with a full page app install banners, the experience would surely be annoying.
Taking a note on that, Google from November 1, 2015 will no longer consider such pages as mobile-friendly. This step is taken to ensure that Webmasters adopt a user friendly way when promoting their Applications.
Google on its official blog post said, “mobile web pages that show an app install interstitial that hides a significant amount of content on the transition from the search result page will no longer be considered mobile-friendly. This does not affect other types of interstitials. As an alternative to app install interstitials, browsers provide ways to promote an app that are more user-friendly”