Google could have bought it; but look at the products it buys.. they either make it google only, incredibly intrusive into your personal life, and primed with adverts, and then shuts down after. The only way to make sure a company dies is for google to buy it.
Gee.. I didn't know Android, YouTube or Where 2 technologies (i.e. Google maps) are dead already.
/s
Why would google buy it beyond charity?
Google tried to do code hosting before, so they must see some value in it.
For GitHub's developer users/community, same as Microsoft.