I don't disagree, but few non-techies will be able to download an image off of an FTP server or mount an NFS share. Thats where such a service adds value.
“What’s a filezilla?”
“go here, drop files there” instead of “download this, put this here, connect, drop your files here” makes the difference between people using your service and not using your service.
Doesn't mean they could not learn that it is not. I think that developers underestimating users is a problem. "They are too dumb to run a desktop app, so let's put everything in the browser" is a weak argument to me.