Wikipedia. Most authors in the western cannon are descendants of aristocracy.
Further, to address your own point, they are not even the representation of successful authors. There's thousands and thousands of successful authors that aren't even near to being close to the gates of the Western canon.
In the 20th century, there have been hundred of thousands to a million different titles published. If even 10% of those authors made enough money to be considered a living wage, it absolutely dwarfs the number of authors in the cannon, which is on the scale of 100s, not thousands.
If the cannon is your standard, your standard excludes almost the entire industry.