Because the women never officially retire. They can't induct Seles, Capriati, Pierce...etc...because they all say they might come back.
they don't have to be officially retired. here is the rule:
Recent Player Nominees (3)Eligibility criteria for the Recent Player category: Active as competitors in the sport within the last 20 years prior to consideration; not a significant factor on the ATP or WTA tour within five years prior to induction; a distinguished record of competitive achievement at the highest international level, with consideration given to integrity, sportsmanship and character.