They do appear on the mobile app. One person out of the hundreds I follow uses them, so therefore I am reminded that they exist, even though I never watch them. If that person happened to stop creating them, I would not know what they are or that they exist.

You would, because the app will still waste the screen space for the fleets bar even if nobody is using it, just so it can push the button for creating a new one in front of you all the time.