GitHub means tying your company's incredibly valuable central assets to a 3rd-party hosted service, despite the service being brain-dead-easy to host locally.

If you're avoiding servers, that also means that you have different accounts for every SaaS service replacement you use, and administering permissions and accounts means a lot of extra and pointless labor.

Using custom code to facilitate your business' processes -- such as server-side plugins for things like your source control -- becomes impossible.

Business processes become dependent on SaaS + data dependence that can't easily be exported from the SaaS services, and you're paying out the nose for them every month -- locally licensed software is cheaper, for quite obvious reasons, all across the board.

All so that you can avoid a once-in-N years failure of a hard drive and running apt-get?

No thanks. That's an insane cost/benefit analysis.

Server administration should be easier than it is, but it's not hard, and I'm not about to make every other business process worse just to avoid it.