Female costumes in SF and fantasy tend to cater for the mostly male audience rather than practicality. Some of them even have high heels and they don't seem too bothered about shielding their skin given how much is exposed.
Not sure it's related, but have you noticed the difference in male and female athletics gear? The women tend to show more skin there, but you would think that would be about practicality.
Well women's beach volleyball, they are practically wearing lingerie. Sure it's cooler and skin tight helps keep the sand out so that one I think is practical.
I've noticed women have started wearing leggings into office settings. So now there is no real difference between the workplace and yoga class, at least from the waste down.
If it's about practicality then why are the guys not in skin-tight stuff too? I'm sure the optics have a bearing on things.