I mean I think it's useful. It answers the question, "what percentage of the time can I rely on every part of GitHub to work correctly?". The answer seems to be roughly 90% of the time.
Nobody cares about every part of GitHub working correctly. I mean, ok, their SREs are supposed to, but tabling the question of whether that's true: if tomorrow they announced a distributed no-op service with 100% downtime, you should not have the intuition that the overall availability of the platform is now worse.
I don't use half of the services, the answer is not straight forward
https://mrshu.github.io/github-statuses/