Seems to me that there are two focuses in Torah study: (1) Study in order to know how to relate and respond to your circumstances (i.e., practical study of both halacha and hashkafa in order to act properly in a God-focused, God-like manner in all situations); and (2) Purely theoretical study.
It seems that while men have a duty to engage in both kinds of study (though theoretical study can never replace or make up for a lack of practical study, since without practical Torah knowledge you won’t be able to act as you should), women are obligated only to engage in practical study (limud al minas laasos), in order for them to know how to act in every situation in which they find themselves.
In times past, the very limited role of women meant that they were unlikely to encounter any great variety or complexity of situations to which they would have to respond in a way informed by knowledge of Torah. They had to know how to keep a kosher home, keep shabbos and yom tov, daven, ect. This could be accomplished with rudimentary halachic instruction, mostly obtained without book learning by watching their own family while growing up. Of course, as the world became more complex, and a woman’s role became more varied and public, women became more likely to find themselves in real-life situations similar or equivalent to those face by men. Women thus needed to have a borader and deeper Torah-knowledge base on which to draw in order to know how to deal halachicly and hashkaficlly with all the circumstances that they would encounter. This cannot be accomplished by learning a little kitzur shulchan aruch, chumash with ramban, and some mesilas yesharim. It requires serious study of a broad range of text in order to inculcate the rules, principles, and methods of halacha, as well as the Torah values, ideals, and objectives worked out in hashkafa.