It's just marketing people playing on stereotypes.
"So easy to use, even a woman, casually at home, can use it!"
And how do you say "casual" without exerting too much effort? BARE FEET!
I guess they could be even more forceful with their message though - instead show her lounging on a sofa, legs not shaved, hair greasy, basic shorts and a tanktop on, rule-34 photoshop of the Brawny guy as her desktop background, and bare feet... The marketing department is then saying, "She's using it in a casual environment, do you get it now?!"
You get the same marketing approaches all over - "Oh wow, a woman is using this wrench! That must be a really easy wrench to use!"
or
"Oh wow, that huge rough-looking guy is using this wrench! This thing must be tougher than a gorilla with roid-rage."
Also, Dell: Your new marketing campaign. Right here.