Firstly I would like to start with the a definition - to write. Writing is to form (letters, words or symbols) on a surface with an instrument such as a pen. Writing is also to compose and set down especially in literary or musical form. Also to relate or communicate in writing.
Therefore, a writer is one who writes especially in occupation.
Occupation is one's regular source of livelihood or a means of support. One who occupies hours of their day making an imprint on paper is a writer. Changing the physical layout of that paper to relate or communicate thoughts to another person. These words hence defined are interesting because they are so common that when their meaning is explored new perspectives open to the observer.
Then what is a writer? Why are there writers? Who is a writer?
In definition, a writer is someone who occupies a large portion of their day creating consistent forms on a piece of paper/computer screen. These forms are a language be it English, Spanish or musical. So, is all writing the same? Clearly not. Then what purposes does it serve? What is the difference between someone who writes law document and someone who writes novels? Both are relaying their thoughts onto a blank canvas. The law writer uses language to clearly state his idea so other people can understand the document. The fiction writer uses language to create a new world that the reader can imagine and see.
Then what about a diary writer or a journalist? Her writing is charged with emotion and personal drama and is often meant to be secretive. Perhaps, this kind of writing also helps the writer skim the lingering fat from the top of the stew.
So why be a writer? To communicate ideas, clear one's head, make a lasting impact even if its only on a thin piece of paper, make a stand and state an opinion. Yes! these are great reasons. Still there are many questions that are fun to explore and will be pursued again later.