It took many decades and two wars for women to be able to "get away with" wearing pants. They were adopted for practical reasons as women entered the workforce (skirts are more likely to get caught in factory machinery), and abandoned again when women exited the workforce post-war. Until the women's movement, pants on women were only tolerated when they were considered necessary.
I don't understand how men wearing dresses works as a comparison to women wearing pants, as there hasn't been an equivalent attempt by men to adopt dresses as everyday attire.
Regardless of the history behind the current situation, the fact remains that women are more free to wear "male" clothing than men are to wear "female" clothing.
