This is why it pays to have your own source repositories in the cloud. It is kind of shocking that many people with the awareness and means are too cheap to pay for a GitHub private repo. I personally could not risk a careless sysadmin deleting my repositories or (in this case) going down for any length of time.
The obvious answer is to have both, but smooth synchronization isn't always easy or even available.
Even if your own solution had better uptime, you still haven't shown that it's worth it. GitHub is far more than just a git repo on a server.
Second, it is completely worth it. GitLab is better than GitHub, so that definitely makes it worth it.
I'm right there with you, but it doesn't make sense for small teams. Once you get past a point, it starts to make sense to self-host some stuff.
Is there a managed hosting provider that would host all this stuff for you? Like, say "I need GitLab, Jira, Active Directory, and X, Y, Z" and they come back with "$XXX/month for 10 users"?
Them going down is still a problem if you're using Github as part of your daily development or deployment process, of course.
I use gh pages for the static parts of my own site even though I have a web server (which I use for quickly sharing files and whatnot) because GitHub is less likely to leave things broken than I am.