Well, you can access the AMP version of the page from anywhere, not just Google search results. I could see apps that use an in-app browser serving the AMP version of a page, instead of the full version, for instance. I guess we'll see?
I'm aware that it's technically possible but was realizing that, as a fairly active mobile web user, I had never noticed AMP in use except for Google search results.
i could see other apps that use a native browser preferring the AMP version. something like yelp, that lets you click through to the source page, for instance.