I fail to see the difference between public on github or public elsewhere.

No public version control. No issues or pull requests or other social features. Like every project, more or less, before GitHub or Sourceforge.

IME, on GitHub (or the other major public repo services), it's far more likely than not that I can pull up an old version of a project from 10 years ago if I want to experiment with it. (In case other old things used it as a dependency, I really want to reproduce an old result, etc.)

On the vast majority of other distribution platforms, it's at best a 50/50 as to whether (a) the platform still exists with any of its contents, and (b) the authors haven't wiped all the old versions to clear up space or whatever. The former typically fails on academic personal websites (which generally get dumped within 5-15 years), and the latter typically fails on SourceForge-style sites.

That is to say, I am not a big fan of the popular alternatives to Git repos as a distribution method.

codeberg is run as a foundation with the explicit aim to help open source projects prosper

github is run by microsoft to sell tools to your CEO with the ultimate aim of making you redundant