[danielrakh]

There's two points to this:

The first technical: When you search for something in Google or Bing you are being surfaced information related to your keywords. Whether that would be an article, a web app, a blog...etc When you search for an App, you are being surfaced an application to solve a certain task.

The second is behavioral: We have conditioned ourselves to use Google to find an answer to our question. In that case, Google is an app we use to find answers to our questions. We have also conditioned ourselves to use the App Store as the gateway to find a certain experience for our smartphone. The average consumer can't differentiate between a web app or a native app, they just know that in order to get an experience on their smartphones the app store is the place to do it.