So the answer is historical socio-economic factors generally preventing women from (1) dedicating themselves to a craft, and (2) from being recognized and remembered even when they do.
Where "generally" means pretty much "always" until a few years ago, and still a lot today.
And not only in literature, of course. Lise Meitner, Jocelyn Bell Burnell and Rosalind Franklin are some very famous examples, but there are many, many others.