Because sometimes it's the only way to get published.

When I first started writing in the 80's, my agent sent my first novel to seven publishers under my real name. All seven were rejected immediately, without the usual editor's coffee stains, smudge marks and what not on the manuscripts. I had a hunch then that it was my name. You could tell it was a woman, and in the 80's, I don't think many woman wrote horror novels. So I adopted a non-gender name--Dana Reed--and had him submit the novels to one of the same publishing houses again as an experiment. And guess what? Two weeks later we received a letter stating that, "if Mr. Reed is willing to change parts of his manuscript, we'll consider it for publication." So, Mr. Reed changed the manuscript as ordered and they bought that one and the next after reading a three page outline for the second novel. In all, seven were published.

At the time, I knew men who wrote romance novels who used names like 'Desiree' something or other. They were writing out of their field and this was the only way to get published. Of course, there's a downside, such as the woman who was infuriated to learn that I was also a female. She'd built up a romantic fantasy with Dana Reed just reading the novels. When she came to a signing and met me, she was infuriated.

Authors at that time were also told to change their names on manuscripts if they had a long, confusing and unpronouncible name. Today, however, some things have changed for the better and I'm glad that authors are not always forced to adopt pseudonyms in order to get published. Then again, there's the downside. You never know what publishers want in the way of names. So if your manuscript comes back with that unread look--no pages dog earred from being flipped, no careless smudges--and it still looks as neat as the day you submitted, think about your name. Especially if you've submitted to a publishing house that doesn't require the use of an agent, and there's no covering letter of explanation, then experiment as I did.