Fear of rejection. Putting yourself and your work out into the world is hard enough, now we have to get used to being rejected too? That in and of itself has caused many writers to stop the story they are working on to move on to other ventures.
For writers who want to go the traditional publishing route, at some point, you will need to write a query letter. A query letter is a one page letter to a literary agent or publisher, giving specific information about the project you are trying to get published.