If you're writing for the joy of writing (intrinsic motivation) and then start getting paid for it (attaching an extrinsic motivation to it) the original "for the joy of X" tends to get lost.
It isn't a "who wouldn't" but rather a "why would you".
Assuming that was a rhetorical question, but since there is a whole "homo economicus" theory of mind out there I'll answer anyway; An actor with other incentives beyond just monetary ones, like physical, social, or philosophical incentives.
Who wouldn't?