"Womens" is actually a pretty old category for sizing, with the smaller complement being the "Misses" sizes. In the early 20th century, Misses pattenrs were intended for teenagers and had smaller bust-to-waist proportions, and then Womens were for more adult proportions and styles. Over the last hundred years or so the Misses sizes grew larger (partly to flatter customers and partly as people got taller and bigger), and the Womens range was pushed out to become today's plus size range.

Also I'm 5'9" and pants are rarely long enough, until I go into expensive trendy stores and they're all too long. Sizing is so weird.