Git is designed so that you always have the full code you're working on copied to your local machine. Github being down for a short time from time to time should be only a minor inconvenience.
Sure, but GitHub is much more than a git repository. Otherwise companies wouldn't pay for it.
As the centralized git repo, it allows devs to collaborate, by exchanging code/features, tracking issues and doing code reviews.
It also provides dependencies management ("Package") and code building/shipping (GH Actions).
Sure, if you usually spend one day or more writing code locally, you're fine.
But if you work on multiple features a day, an outage, even of 30 minutes, can have a big impact on a company because of the multiplier effect on all the people affected.
