Here's an excellent short essay on why more people should write.
You should write because when you know that you’re going to write, it changes the way you live.
That’s the promise: you will live more curiously if you write. You will become a scientist, if not of the natural world than of whatever world you care about. More of that world will pop alive. You will see more when you look at it.
Not only will you notice things more, you'll remember them better.
When I’m regularly writing, I feel like a photographer walking around with a camera strapped to my neck. I’m looking for a good picture. And when I see an image I like -- a brilliant color, a composition of interesting forms -- I'll appreciate it and focus on it.
But rather than images, I'm looking for ideas.
I do pay more attention to the world. I may not remember things better, but I'm much more likely to write things down so that I will recall them later.
There's one negative. I'll hesitate to read something because I know it will be rich with ideas. It is bound to generate writing. So instead of simply enjoying the reading, I'm thinking of the writing work that will follow, which is indeed work rather than purely pleasurable consumption. Reading is somewhat spoiled.