Two notable differences between MLA and APA include the content of the parenthetical references and the placement of publication dates in the "Works Cited" or "References" lists. These differences are impossible to standardize because they are rooted in the rhetorical needs of humanities scholars on the one hand, and social sciences researchers on the other.
Humanities research revolves around presenting a close reading of a specific text. Dates are important reference points for context and establishing the primacy of a specific version of a text, but in the midst of reading and interpretation the words on the page, the specific page, are the center of attention.
Social scientists center on the gathering and analysis of data and the building of theory rooted in data. The words on a specific page of a published article are not nearly as important as the report of results and conclusions represented by the whole of the article. So specific page numbers are only incidental. The year of publication, though, becomes important because it places the one report into the context of all the reports in the particular line of research.
So we will always see page numbers in MLA and years in APA, and that is the way it should be. And students should have to learn the style for the discipline they are working in, so they can better learn how to work, that is use books and other sources, in that discipline.