Wow, that’s a sweeping generalization. Have you never read about writers that work hard to make sure they’re getting the message across clearly?
Many people who force themselves to write every day do so to get out of the loop of only writing when they “feel” like it. Writing when they’re “in the mood.”
We don’t wait for the mood to strike to go to work, but we do that with things that society typically devalues, like writing and painting and many creative arts.
Relegating the arts to when we’re in the mood is why so many creatives have to get day jobs that they hate. And that (likely) comes from a lifetime of people telling creatives that it’s “no way” to make a living. Because artists starve, you know.
Developing a daily habit isn’t about money or attention, it’s about developing a creative discipline. Once the habit is there, the work becomes enjoyable again.
It’s not just writing, either. When a person first gets into fitness (for example) — those initial trips to they gym aren’t always fun. They have to “make themselves” go. But one day, when the habit is formed, they discover they’re loving it, and the end result of developing a discipline.
I can’t speak for everyone, of course, but that’s the place most of the writers I know come from.