Typically, the most common use of alternate pen names is when one story's content will sour readers on your work. Thus if someone writes action adventures, and then decides to write a romance, they'll typically use a separate name, so the two sets of fans won't overlaps.
I did that for my one gay erotica story, which served as a tribute to my brother, as it focused on a core theme of his which isn't heard much anymore. I didn't do it when I crossed over from Sci-Fi to write a mystery novel, but the newer genre attracted additional fans who then sought out my older SF stories as well.
Obviously, if you're writing romance, you typically pick a feminine name, while for action adventures or gumshoe stories you stick with short masculine names (like Quirk Jones, or Banger McGee).
If anyone wants to expand their range, have at it, but don't expect your followers to eagerly follow you down a particular rat hole if it differs from your other works substantially.