What makes people want to write something that is not for immediate practical use (e.g. school/work report, letters of invitation)?
Part of it, especially for literary and philosophical types, is no doubt fame, fortune and the possibility of immortality. Who could resist the thought that perhaps, one day, one’s writing will be pored over by scholars like any little scrap of paper by Shakespeare or Kant?
More prosaically, writing also helps solidify memory. A trip that is not written about soon gets forgotten: the dates are confused, the sights blend gradually into one another. A written record gives the memory a freshness that preserves something that photos cannot fully capture.
It clarifies thinking too. Some might go as far as to say writing constitutes thinking; but at least it evidences it.
The activity of writing everything out forces us to set out the details and saves us from having to remember them. It also forces us to set out explain oursevles from the perspective of someone who is looking at everything afresh: which is likley quite different from the original context and background.
In “Write and Write-nots”, Paul Graham goes almost as far as saying that it is imposssible for someone to think clearly if she cannot write clearly: when one is not writing, one merely thinks one is thinking.
I wish this is true: I may not write very well, but I certainly write (a lot) more than others. I do not think it helps me think more clearly though: I have met too many clear thinkers who are miles ahead of me, but who just don’t like to write.
But perhaps the real advantage of writing to thinking is this: it saves the thinker from having to find the right audience or conversation partner.
Outside of work and certain very close friends, it is not straightforward to find someone to share my exact same interests. While poor conversation skills is in part to blame, part of the reason must be that they are just not very interested in the exact same topic I am interested in at exactly the same time.
For example, I am all over Robert Nozick at the moment, but while he is one of the more famous philosophers in the 20th century, there are dedicated philosophy enthusiasts who have only heard of, but not read, him. Similarly for Amia Srinivasan, who (despite her Chair at All Souls College, Oxford and wonderful LRB esssays) is not read even by some philosohpically-minded LRB subscribers.
So rather than trying to find a conversation partner to discuss their ideas (likely a futile task), better to simply write about them and have in my mind the perfect reader: someone sympathetic and knowledgeable, who would follow the argument where it leads but offer pushbacks where they are due.
After all, when we read, we (generally) give the writer our undivided attention: how often do (can?) we do that for people around us, when there are things to do and phones to look at?
The yearning for that undivided attention: perhaps that is why people are attracted to the idea of writing/being a writer, more than fame or fortune or any other benefit.