> Your mail provider is failing? It'll be up in 5 minutes tops, or your disk is full probably, go handle it yourself.

Well until you deal with email deliverability issues, which are staggeringly widespread and random. Email were great to send quick patches between friends like you'd exchange a USB key for a group project. For a project the size of Linux? It doesn't scale at all. There is a reason why Google, Meta, Red Hat, and [insert any tech company here] doesn't collaborate by sending patches via email.