Literary theorist Roland Barthes said of the difference between an author and a writer, "The former performs a function; the latter an activity."
What is an author's "function"? To go on lecture tours, like Mark Twain? To be on Today? To appear at signings and banquets? To inspire writers who aren't at the touring/Today Show level yet? Twain , the most famous touring author, wrote (1896):
I got horribly tired of the platform toward the last -- tired of the slavery of it; tired of having to rest-up for it; diet myself for it; take everlasting care of my body and my mind for it; deny myself in a thousand ways in its interest.
Seems that without actively writing, an author is decorative -- they do call it "an appearance" -- or at best a pawn in his own money-making game.
And doesn't a writer have a function as well as an activity? Like, to stir people's minds? To entertain them? To educate? To stand for something?
Those literary theorists...I'm sure Barthes explains his statement well and in depth, but I read more than enough theory in the 1980s, before we all found out that literary theory ("literature means nothing") was the brainchild of a former Nazi collaborationist, Paul de Man, who in the rest of his lifetime neglected to mention that rather telling fact.