We're in the process of moving our git repositories to GitHub. There are two main reasons for doing so. The first is that we want to reduce load on our Ops people. While managing internal git repositories does not take lots of Ops time, it's one of many chores they do and which collectively take lots of their time. Managing git repositories through GitHub (or some other code hosting service) is one of the many tasks that developers can do by themselves, thus reducing load on Ops people and friction between developers and Ops personnel.
The second, more important reason, why I'm pushing for migration to GitHub is that GitHub is becoming de-facto standard way of storing and managing code. Almost all the start-ups I know rely on GitHub for managing their source code and there is a huge ecosystem developing around GitHub to help people with every possible issue they might have. Managing our own git repositories would exclude us from this ecosystem and preclude us from learning from good practices of other start-ups.
As with any migration we have some issues with GitHub to resolve, and some guys are worried about our dependence on external storage of our code. But just like end users, also developers and Ops people will have to adapt that everything is moving to cloud, including our development environment.