I don't believe it is that clear cut. I think you are ignoring the fact that native developers have frameworks of their own. Using Boost, GTK+, or Qt gives various layers-of-thickness over the OS so the native code is portable. Some, like Qt, also cover mobile operating systems as well as desktop ones. These frameworks are not young either; so while websites had browser-specific-detection-code (thanks to IE), native apps were already running cross-platform by leveraging frameworks of their own.