Bryan Caplan argues the 50/50 husband/wife domestic work norm runs afoul of the principle of comparative advantage.
What if a man has a much higher wage than his wife, but can't clean, cook, or shop to save his life? Should he still do half the cleaning, cooking, and shopping? Wouldn't husband and wife alike be better off if he specialized in bringing home the bread, and she specialized in baking it?
Well, maybe not. Maybe the wife would be better off with the sense of increased social status and independence that comes from labor market participation. Maybe the wife hates cooking and cleaning and would like to realize some of her potential as a human being through satisfying work that engages her talents. Imagine a possible world in which Bryan makes less than his wife. Is he making pot roast?
Moreover, part of the 50/50 point is about social expectations. If girls are expected and encouraged to semi-specialize in domestic labor and boys are expected and encouraged to specialize completely in some kind of non-domestic career and always burn the toast, it comes as no surprise when it turns out that it is generally more efficient for the husband to head to the office while the wife heads to the kitchen. But in this kind of case, the efficiency of the arrangement is evidence of a prior injustice, not of general hunky-doryness.