New writers often ask, “Do I need a pen name?”
The answer, usually, is “No. Unless, of course, you do.”
What do I mean by that? Let me unpack a bit.
There are several reasons why a writer might have a true need for a pseudonym, of which security is the biggest. A writer who is engaged in saying things about powerful people and entities to which those people and entities might take exception, for example, may choose to write under cover of a nom de plume, as Jonathan Swift did when he wrote a series of political pamphlets about English fiscal policy in 18th-century Ireland under the pseudonym of “M. B. Drapier.”
Similarly, a writer whose regular employment involves working with or for people who might look askance at one of their employees having a commitment to something other than the job might use a pen name to keep the two lives separate. Writers who work for the government, or for the military, also fall into this general category.
Then there are the writers who, for whatever reason, don’t want their friends, or family, or co-workers to know that they write — or sometimes, to know what they write. Schoolteachers, for example, are expected to be as above reproach as Caesar’s wife — if you’re teaching eighth-grade English as your day job and writing steamy romance novels on the side, you probably don’t want the school board to catch on. (Not even if half of them are devoted readers of your other persona’s literary output. They’ll just ask for your autograph out of one side of their mouths and decline to renew your contract with the other.)†
Sometimes the decision to use a pseudonym is driven by economic reasons. An author whose previous output had a lackluster reception, or which fell prey to one or another of the assorted bad things that can happen to good books, may choose to start over under a pseudonym. Opting for this course of action used to be a closely-guarded secret, rather like going into the Witness Protection Program, but readers are more savvy, usually, than publicists think, and the cats in those cases never stayed in the bag for long. These days, the economy-driven pseudonyms are more about what the marketing types would call “establishing brand identity” — this is the pseudonym for the author’s YA work, and this is the sf/fantasy pseudonym, and that one over there is for mysteries and thrillers, but everybody knows that they’re all the same writer at the keyboard.
And finally, you get the writers who chose to write under a pseudonym because they don’t like the name their parents stuck them with, or they like their name just fine but know in their heart of hearts that nobody outside of their particular ethnic group is ever going to be able to pronounce it, let alone spell it right or shelve it correctly in the bookstore, or they prefer to draw a hard line between their writer-persona and their everyday-persona for some reason that is private and particular to them.
†My parents were teachers. It didn’t leave me with a high regard for school boards or school administrators in general.
Or, some genres come with an expectation of a certain gender presentation for writers. It’s no longer critical in SF the way it was decades ago, but mainstream romance authors are generally expected to be female, and there’s a pattern of m/m romance authors using male or androgynous pen names, even if they’re very open about using female pronouns in author bios and interviews.