[Macha]

> ...until the project decides to switch to another hosting provider

Or decides their github username looks better with an upper case letter (https://github.com/sirupsen/logrus/issues/570). Or for people who use their real name as their github name, updating their username after marriage, divorce, gender transition or whatever.

[bmicraft]

Or they create a github organisation (which might be even worse because the old repo probably still exists but could be stale)