You don't have to, package maintainers and developers do. Flatpak gives them the tools to do this. Flatpak solves a lot of other problems like making program in

You don't have to, package maintainers and developers do. Flatpak gives them the tools to do this. Flatpak solves a lot of other problems like making program installs a user level task without touching the OS. Which is needed because in the future the OS will be an immutable image.