This is explained by the concept of comparative advantage. If a man is both a potentially better cook and also has more valuable manual labor than a woman (a likely scenario, although I say "potential" because a woman who cooks everyday is almost certain to be better than a man who never cooks) it still makes sense for the woman to cook because the difference in the value of the woman's cooking and the man's cooking is less than the difference in the value of the woman's manual labor and the man's manual labor.
If company A can make a steel girder for $200 and a glass pane for $100 and company B can make a steel girder for $300 and a glass panes for $120 then assuming company A does not have sufficient labor to make both it makes sense for them to focus on steel girders and buy the panes from company B despite company B being better at neither product.
This is explained by the concept of comparative advantage. If a man is both a potentially better cook and also has more valuable manual labor than a woman (a likely scenario, although I say "potential" because a woman who cooks everyday is almost certain to be better than a man who never cooks) it still makes sense for the woman to cook because the difference in the value of the woman's cooking and the man's cooking is less than the difference in the value of the woman's manual labor and the man's manual labor.
If company A can make a steel girder for $200 and a glass pane for $100 and company B can make a steel girder for $300 and a glass panes for $120 then assuming company A does not have sufficient labor to make both it makes sense for them to focus on steel girders and buy the panes from company B despite company B being better at neither product.