Why Linux and Git development happens on mailing list instead of GitLab for example.

https://programming.dev/post/1773451

Why Linux and Git development happens on mailing list instead of GitLab for example. - programming.dev

What are advantages of it and also how said mailing list works? (In case of software development)

Probably because it works and there hasn’t been a strong reason to change it.
It would work better under these modern methods, but the fallout during changing would be too much to handle