As an extreme example, today I needed to combine parts of two files into one and decided that
cat foo bar > foobar && mv foobar bar && vim bar
of all things will better keep me in the flow than either googling how to insert one file into another in vim or starting up TRAMP.EDIT: Found http://www.fifi.org/doc/tramp/tramp-emacs.html which mentions that TRAMP started development in November 1998. I would have been getting that advice in late 1997 or early 1998, given when I started my Unix class at college. So the answer appears to be that the advice was actually correct at the time, but superseded sooner than I thought it was.
Of course, if your problem is "/usr won't mount", then it's likely that the ftp server isn't running either, so the advice still makes sense.