The true elegance of writing contests as an author is that you never have to mention the ones you did not win; only the ones you won. A shiny list of competitive writing contest wins that you have been awarded will impress readers, agents, and publishers alike.
I like to write short stories as a change of pace from my other writing. Sometimes I enter contests with my writing. I find it a good way to push my writing skills and keep myself growing as a writer.