That's just lazy. How that works is on any shell man page. If you fiddle with it a little bit you figure it out:

    set -- "foo"
    echo $#
    set -- foo
    echo $#
    set -- "foo bar"
    echo $#
    set -- foo bar
    echo $#

Of course, people just want their commands to run and not learn a whole new language. Then I come back to my initial point: the language itself is small and easy to remember once you internalize it, what makes it scary is the umbrella of different command line utilities that _seems_ to be a part of the language but it's not.