Because success as a professional hinges on remuneration and the act of selling something, and people who are known as authors "supporting" themselves on their writing are held in radically higher esteem than those who write "on the side" but make the majority of their income doing something else.
More than that, The Great Creative Meatgrinder tells talented, impressionable young creatives that if they build it they will come, that talent will win out over mediocrity, that it took you 20 years to become an overnight success, that it's all about strength and perseverance. The Great Creative Meatgrinder does not tell these children that they'll be doing it while asking if you want fries with that while the stories they'll hear will all be about trust fund kids who get a new Macbook every year because uncle Chester loves "having a writer in the family" and drive a two-year-old BMW 7-series because Ivanka hates it when the Fullertons have a newer car than she does. And they'll get to go to meetings at places with $500 bottle service that will sell you five bacon-wrapped dates for $12 because - and here's the other thing they won't tell you - the rich children pick expensive places purely to keep the proles out.
Everybody loves Anne Lamott. Bird by bird. Page by page. It's about the work, which you can do while being divorced, while raising a kid. Few people mention the fact that Anne Lamott started hounding her dad's agent when she was in her teens, and didn't get anything published until said agent eventually got something sold when she was in her early 30s.
Know how many aspiring young writers get an agent that will read their drivel for fifteen fucking years? If you guessed "the ones whose parents have made their agents a lot of money" you didn't need to read this article.