Before men started wearing the crotch-covering legging we call trousers, everybody wore skirts in one form or fashion (see also: loincloths, tunics, togas, kilts, etc.). And why not? Skirts are far simpler to construct and facilitate more cooling air flow to the nether regions, which would've been a godsend in the pre-air conditioning days. But then, thanks to the rise of horseback infantries, trousers (see also: breeches, codpieces, tights, etc.) became the below-the-belt manly uniform of the masculine masses.
Western women, meanwhile, continued wearing skirts, and not just simple wrap-around numbers. We're talking multi-layered, heavy, floor-length ensembles often further supported and puffed out with the assistance of cage crinoline, petticoats, bustles, or other clunky foundation garments, depending on the era (see also: corsets).