Whenever GitLab, Codeberg, BitBucket and, mostly, GitHub goes down, a lot of the software and websites you use can't be updated, including dependencies of your software that you're pulling from npm, for instance.
Finally, companies use code forges mostly for the ease of doing code reviews through Pull Requests/Merge Requests. Developers rarely, if ever, actually merge branches locally, before having it reviewed by peers in one of these code forges.
Teams I've worked on for the last several decades aim to push 10-20 builds per day to external alpha testers, so any downtime in Github is going to be an impediment.
That isn’t as convenient as an all-in-one tool, and might not be what the user you’re responding to is doing. But it’s doable.