I can see two opensource groups that benefit from this. Maintainers can produce quality packages that don't vary unintentionally between target systems with less effort to produce. Package consumers can rely on having the same quality packages on varying systems. I use Ubuntu Server mostly because its packages are highly consumed. If I could get the same packaging on a different system I wouldn't have to worry about arbitrary variations not related to the distro but different just because it's produced through a separate workflow.