We support snippet version history in the Teams plan. Of course, it's not as sophisticated as commits in a version controlled repository 
There have been few requests in the past, but there's no plan yet, because it can cause unexpected confusion among new users.
Snippets (and Text Blaze) is optimized towards building reusable templates. At the core of this are snippets with plain text or styled text. The next climb up are form fields and key presses. The next climb is basic if/else and repeats logic. The most sophisticated usage is regex/math on variables/etc. As you would expect, most users are on the first two layers on this journey, because it's a steep climb at each step. So yes, most users wouldn't see their creation as "code".
Now from the engineering perspective: The snippets model is very different from code. I'm sure you already figured all of this out But to reiterate for anyone else reading: Think JavaScript (so it can interact with site), but 1. much more forgiving in terms of errors 2. functional like Python 3. not imperative at all (every variable update refreshes the entire snippet) 4. recursion or even recursive assignment are not supported (we can probably tweak it to support point 4, though)
Your suggestion to synchronize snippet updates with GitHub is interesting. If you're really interested, you can probably implement this with a bookmarktlet and manually trigger an update to a private github gist via their api. We can get the editor plain text snippet contents in by using document.querySelector('.ql-editor').innerText. It's not ideal, though.