Github is more than a remote host for git repositories. It's become one of the major CDNs for software distributions. Github Pages host a majority of static sites that developer use. You won't be able to use Cargo, Nix, Scoop and other package managers right now because their registries have a critical dependency hosted on Github.

This is not to mention all the projects that rely on Github for project management, devops, community and support desk.

GitHub is also very international, I doubt isolated netziens like those from China are shielded from this outage. I imagine very, very few software shops are unscathed by this. The whole affair is very on brand for 21st century software which is to say pitiful.

The key difference is being able to mirror communication channels. While you can continue to work fine with your local repo, the only way to share those changes are via another forge, or sending patches through some other channel. Having another forge to distribute code is generally more ideal.