Techcrunch could be delivered as a PDF. I get it on my Kindle.

Just as most new web sites are not startup companies, most existing web sites are not apps.

The distinction and difference is that a software application helps a user perform manipulation or transformation of data as useful work.

Most websites, despite simple interactivity (e.g. search), are still published as "content" for consumption within a content access application, not for manipulating work|play|creative output.