"Having to use"? It was suggested to Rowling and she decided to go with the advice, but women have been successfully publishing under female names at least since Sappho. Mary Shelley? Jane Austen? Maybe I'm biased because in my genre, there's Leigh Brackett, Marion Zimmer Bradley, Ursula K LeGuin, Octavia Butler, etc.She countered,
Currer, Ellis, and Acton Bell? You might know them as the Brontes. George Eliot? J.D. Robb? A.M. Barnard? Isak Dinesen? George Sand?And I replied,
I always wondered when the Brontes were outed, because I never encountered them as the Bells. So I just googled it: it was in July, 1848, and it was their choice. Somehow, they managed to succeed under female names, just as Jane Austen and Elizabeth Gaskell had before them. I haven't found much about this, but it would appear their books have been published under their own names since 1850.
George Eliot's first publication was in 1856—after the Brontes were known as the Brontes. Of course, Eliot had a right to pass as a man in the belief it would be better for her literary career, and we can't know whether she was right to think she should use a man's name. In any case, she outed herself in 1859, when her first novel came out, and she doesn't seem to have suffered from having done that.
What's tricky about the women who wrote using initials is men have done the same. C. S. Lewis, B. Traven, J. R. R. Tolkien, etc.ETA: I seriously considered using my initials for my pen name because I was a pretentious git when I was young, and if you think I'm still one, I can't really argue with you.