Why writing has the potential to find success and satisfaction in honesty
I don't know about you, but I find that I am far more comfortable talking honestly to an audience of one person, than an audience of two or more. Even if I don't know the one person very well, and the two people were good friends, I would still feel that I could be more open with the one person.
It's to do with instinctive empathy. To feel 'empathy' is to identify and understand another's feelings. Why do we experience empathy? To fit into our society. We need empathy so that we help one another survive to further progress our species. But empathy can also instil fear and alienation.
Example 1: there is one person - Bob - listening to Gertrude explain how she likes to walk rather than ride her bicycle. Bob nods his head in an understanding way, and even agrees with her on certain points of her argument, even if he had, before now, disagreed with her. His objective is to fit in with Gertrude because she, like him, is human and he wishes to fit in with human society.
Example 2: there are two people - Bob and Ashok - listening to Gertrude explain how she likes to walk rather than ride her bicycle. Bob and Ashok will listen, but will have another more pressing objective in mind: they wish to empathise with each other's reactions to Gertrude. They are united by both being on the receiving ends of Gertrude's voice. They might (both afraid that the other thinks Gertrude foolish for opinions) look at each other dubiously, and put some effort into predicting the other's responce, and then act upon it. This way, Bob and Ashok will be united, and Gertrude will be left alien to the duo.
Of course, this example is on a small scale. Gertude's opinion could be that homosexuality should be legal in every country, that God does not exist, that God does exist ... whatever. The thing that makes Bob react to her in a certain way, is often due to the fear of what someone else in the room may think of her ideas.
Naturally I have simplified the influences upon Bob. They are more complex than that which I have explained, but the general rule holds. If you get someone on their own, away from the presence of the rest of society's influences, then they are far more likely to consider your argument with a level head. And of course age will affect Bob, too. If Bob were 15, he would be more impressionable than if he were 73.
Now, to get to the point: written language is a silent conversation between only two people - the writer and the reader. The reader will be in their most weakened state of empathy while reading, because they are the only one (as far as they are concerned) on the listening end of the narrative. Sometimes people read for that very reason: they want to empathise with a character and they want to find a voice that will be honest with them, because perhaps they really will understand what the writer is saying as long as they shut their mind to the rest of society.
Films can work in a similar way. But it's the silence of reading to oneself, and the extensively detailed nature of a book's expression, that makes writing the ideal container for the honest thoughts of those of us who do not wish to risk revealing them to two or more people at once.