I'll readily admit that the core of ClearCase leaves much to be desired from a technology, administration and user perspective. Especially in comparison to git. But that's the difference a few decades of progress can make.

But what's built on top of it are definite wins in comparison to git and Github: UCM and lifecycle integration with ClearQuest.

Most developers don't know how/when to branch. UCM at least sets up a structure and process for that. There's also enough out-of-the-box security to control access to everything that most enterprises would care about. This is supported, documented, etc.

Managing an application's lifecycle is probably far more important in a large organization than most people experience in a small project or startup. Integration with ClearQuest allows everything to be tracked.

Since all of this are essentially "add-ons" to a core versioning tool, there's nothing to say something similar can't be done with git/by Github. It's just that they're not available _now_.