GitHub is distributing your Git repository across multiple servers in multiple racks in real time for reliability and availability and is the world's largest Git repository hosting provider. Some nice conference talks discuss this, like from Git Merge: https://www.youtube.com/watch?v=f7ecUqHxD7o and GitHub Universe: https://www.youtube.com/watch?v=DY0yNRNkYb0
Visual Studio Team Services is hosting your Git repository across Azure, and is hosting the world's largest Git repositories. https://arstechnica.co.uk/information-technology/2017/02/mic...
I have my own Git server as well, and I agree that its maintenance isn't very demanding. But I'm not putting production bits on it. My open source repositories go to GitHub and my private repositories go to VSTS - they're providing a level of service that I simply can't match by myself.