You can access data from deleted forks, deleted repositories and even private repositories on GitHub. And it is available forever. This is known by GitHub, and intentionally designed that way.
Technically you can do everything through email, because everything online can be represented as text. Doesn’t mean you should.
PRs also aren’t just a simple back and forth anymore: Tagging, Assignees, inline reviews, CI with checks, progress tracking, and yes, reactions. Sure, you can kinda hack all of that into a mailing list but at that point it’s becoming really clunky and abuses email even more for something it was never meant to handle. Having a purpose-built interface for that is just so much nicer.
Technically you can do everything through email, because everything online can be represented as text. Doesn’t mean you should.
PRs also aren’t just a simple back and forth anymore: Tagging, Assignees, inline reviews, CI with checks, progress tracking, and yes, reactions. Sure, you can kinda hack all of that into a mailing list but at that point it’s becoming really clunky and abuses email even more for something it was never meant to handle. Having a purpose-built interface for that is just so much nicer.