Which authorities permit women wearing "womens' pants", as long as it is covered by a skirt, in lieu of tights in non-athletic situations, for example as a more comfortable, warmer, or even more tznius option? Why do those who forbid the practice in any case hold that way?
It might not be a problem in technical halacha, however it definitely doesn't fit with being a Bas Melech. Every Jewish women and girl is a princess - Dovid Hamelech established this fact in Tehilim chapter 45. Therefore Jewish women have to live up to their essence and dress always in an elegant, regal and royal mode of dress.