The simplified reason is that it creates a social world where anyone can be seen as a hero because they are courageous, or seen as a nurturer because they are nurturing, or a coward because they are cowardly, or a commander because they are commanding, and etc. Not because they happen to or not fit into a gender box that defines the attributes you’re allowed to legitimately exhibit.
Why should we aim for that?
The simplified reason is that it creates a social world where anyone can be seen as a hero because they are courageous, or seen as a nurturer because they are nurturing, or a coward because they are cowardly, or a commander because they are commanding, and etc. Not because they happen to or not fit into a gender box that defines the attributes you’re allowed to legitimately exhibit.