Since the invention of the movie, author salaries have been pretty bad. In the distant past, people like Twain or Dumas could get, if not rich, then very well off just from writing. Back when print was the only mass-market entertainment medium, buy books were IT.
Since the beginning of visual/sonic entertainments that don’t require literacy, literacy and author salaries have been declining. Lots and lots of people who might have bought books in 1885 don’t buy books. Why should they when they can get more bang for their buck from movies or TV? In the 20th century, “Don’t quit your day job” became a universal writers’ mantra because poverty was the most likely outcome of doing so.
Scalzi could have used one example from his own field: Among science fiction writers in the 20th Century, Robert Heinlein was a notable exception to the rule. He became famous among other SF writers because he was the only one who actually made a decent living JUST from his writing. Every other writer in the genre wrote SF because he felt the need to write imaginative works, and he wrote for magazines and newspapers under pseudonyms because he felt the need to pay the utility bills.
Now, books are an interest of only a minority of the population, because books place too great a demand on people. Books require people to be able to read and to think at least a little. And way too many Americans find thinking painful. It interferes with listening to Garth Brooks or R Kelly and it makes them realize that binge drinking and drug use are not sensible. Too many Americans don’t know a damn thing and they hate and fear anyone who does.
