When I used to build app packages internally I also built packages for our own python and ruby versions for our in-house software. The motto was: “system packages are for system software”. We weren’t writing system software, we were writing business software and shipping it, so why be dependent on what Redhat or Debian provided?
Universal packages are just an extension of this philosophy, and is why things like docker and app stores are such a success. Burdening the user with getting system dependencies right is worse than the DLL hell of the old windows days.