Writers who have not developed the knack of writing about topics in which they have no interest for audiences to which they have no emotional ties have not learned to write for the real world.
In the workplace, writing topics are almost always given. A nonfiction writer is rarely free to choose what she or he wants to write about. Of course, freelance writers can pick their topics, but if they pick topics publishers won’t buy, they may end up having to eat their words instead of groceries.
Typically, audiences to whom a writer must communicate are people who don’t share the writers’ background, beliefs, and experience. Often writers must espouse positions they don’t believe in: Writing what students describe as their “honest thoughts” is rarely welcomed by employers.
Writing for one’s self or even for close friends and family isn’t real writing — not even if the topic is astrophysics.