By launcher, I mean Start-menu, launchpad, Application Menu or whatever.
All launcher is a literal implementation of XDG’s Desktop Entry Specification which will scan /usr/share/applications/ for .desktop files. Those files are usually installed via a pkg manager.
.appimage is downloaded by a user rather than through the package manager.
To have an icon on the launcher for .AppImage , a user must conduct extra steps to generate .desktop at that specific path (There are many HOW-TOs written for this mission).
What if launcher vendors can implement scanning of a special folder (~/Applications like macOS), and grab the desktop entry file automatically?
If this can be done, a program can just distribute a .appimage and tell the user to
Download Nice.AppImage and move it to ~/Applications/
This will automatically give all benefits of having .desktop file: