Hi Boyo
Wondered if you had come across any of this reading?
https://appimage.github.io/apps/
and
https://itsfoss.com/use-appimage-linux/
By Devs, do you mean the devs of the software itself, or the devs whom provide us with the Linux Distros?
My guess is with the Linux Distro Devs, they are likely to take a bunch of packages already existing in the Linux marketplace and put the all together in one place, their Distro.
Some Distro Devs take the time to develop their own software, notable examples of this have been Ubuntu with the Ubiquity Installer and the Unity Desktop Environment (although the latter was forked from GNOME), and Linux Mint with the Cinnamon DE.
Software licensing may also be an issue. Much of Linux is licensed under GPL, but in that first link I provided, we also see instances of MIT and others.
Have you made the acquaintance the burning solution, Etcher, yet?
https://etcher.io - it is in AppImage and cross-platform.
I like it for an easy burn of .isos, but a limitation
it has is that it fully allocates the space on your USB stick, leaving no room for Persistence to be added, whereas other solutions do.
Cheers
Wizard