Exactly. The idea that people who have an ardent need for financial support to survive would choose an activity that is statistically unlikely to provide sufficient financial remuneration seems odd, don't you think?

The separation here is nothing to do with "art". It's to do with a person's ability to choose an occupation based on desire/interest or pure financial need. Writing is in the former category not because it's "art", but simply because one needs to be comfortable to have the luxury of taking such risk.

To put it another way: people choose the vocation of writing despite financial motivation to pursue alternative more lucrative undertakings.