If I can't afford electricity to be down, the yes, the business should have generators. I would never put my hosted servers in a data centre without generators, for example, as the stuff I put there is there instead of in our office because it needs a solid environment.
On the other hand, our office servers are on a single circuit and we don't worry about it because a temporary electricity outage just means a few man hours lost productivity (rather than potentially large losses for our clients, leading to bad will and lost business for us)
If a Github outage is so critical to you that it's more than a few man hours lost productivity, then it means you're using it for something you either should have in house or should have adequate backup procedures for. And this holds regardless what you substitute for "Github" in this paragraph:
If it's critical, you ensure you have a backup, as it's virtually guaranteed that there will be some single point of failure outside of your (and theirs) control.
On the other hand, our office servers are on a single circuit and we don't worry about it because a temporary electricity outage just means a few man hours lost productivity (rather than potentially large losses for our clients, leading to bad will and lost business for us)
If a Github outage is so critical to you that it's more than a few man hours lost productivity, then it means you're using it for something you either should have in house or should have adequate backup procedures for. And this holds regardless what you substitute for "Github" in this paragraph:
If it's critical, you ensure you have a backup, as it's virtually guaranteed that there will be some single point of failure outside of your (and theirs) control.