What’s your server’s uptime? Is it highly available? How often do you patch? Do you test them first? How do you keep up with security updates from other software on the machine(s).
How is your security team in general? Do they monitor for stolen credentials? Do pen-tests? Watch for network scans and attacks? Look for weird traffic patterns?
Do you have redundant network links? Backup generators? Do you test them? Sure your datacenter SAYS they have them, but remember when Intuit went down for 2 days a few years ago? I bet they had told their bosses they had generator backups.
Is someone always on call? What are they experts in? How do you get support?
GitHub provides a TON of stuff above a cheap VPS or EC2 instance. And that’s not including the network effects of having so many projects in the same site.