The thing I love most about GNU/Linux distros, from a practical point of view, is that all the software has been made work together, and has been audited by someone I choose.
In the 90s, when I used a proprietary OS, the default video player played all videos. Then I'd install QuickTime, and it would impose itself as default video player plus default image viewer despite it's image viewing capabilities being awful. Then I'd install RealPlayer, same problem again. One would do this via the registry, another would do it via start-up programs, and others did it in ways I never got to the bottom of.
Then I moved to GNU/Linux. I can install ten video players, and they don't fight with each other. What a relief.
If everyone got their Firefox direct from Mozilla, and if the Mozilla developers were told to say nothing about a privacy problem, then who would have noticed the privacy problem? When distros modify packages, that introduces an independent review into the supply chain.