There are many reasons folks don’t write. Lack of talent isn’t one of them.
Thinking they should write is.
It isn’t that they have nothing to say. They do.
It isn’t that they can’t put words together well. They can.
It isn’t what they wish to write is not important. It is.
Thinking that they SHOULD write is the wrong part. Writing isn’t what you SHOULD do.
So, they shouldn’t.