Because some of us use Emacs on a daily basis and don't have vi keys seared into our brains. I know the basics, just for these kind of cases, but given the choice I'd use mg any day over vi.
I think his point is that on most systems, except localhost, you shouldn't be touching the config files with an editor. Those files should be managed by an automated system (config management system). Such as chef, puppet, ansible, salt, cfengine & the lot.