I don't remember the details completely, but shortly after Google bought Blogger.com, they disabled ftp upload to blogger. That seemed to me at the time to be a clear attempt to encourage you to store your website on their servers ... and only on their servers ... without backup on your machine(s).
IIRC, if your website has only a few files and if you don't use Google's website creation tools, you can upload all your files one at a time via some clunky manual interface and keep a local backup. But for most people, with a website of any size, you pretty much have to just trust Google. I didn't trust Google to always act in my best interests then (and don't trust them now). I moved my website to someplace where I could simply upload from my master copy using a simple script. But I'm a techie. This unfortunate gentleman is an artist. How is he supposed to figure out he's dealing with typical system administration (i.e. whackjobs)?
I suppose you could probably update your site the Google way and periodically download copies with wget/curl to keep a backup. But I wouldn't be at all surprised that in the clusterf**k that is today's internet, that is difficult, impossible, or doesn't get all your files.