Who can that attractive girl be?

What is it with men and skirts?

Ok. The Fed-Ex guy, who already calls me "sweetheart" and rolls up his sleeve to show off suntan lines, said I looked very pretty today. Nice enough compliment, and I thanked him. The thing is, I think I look basically the same today as I did yesterday and the day before that. Certainly, from the waist up, my outfit is identical because I wear the same white hoodie every day in my sub-zero office. The only difference, as you may have inferred, is that today I am wearing a skirt. Knee-length grey pleated, vaguely cheerleader-esque, but not overtly sexy. Thanks to my Mary Hart table-as-desk, you can see my legs underneath. No pantless days for me, sadly. My question is, what is it about skirts and dresses that people (not just men) automatically think you look prettier in them? What if I was wearing shorts and showing the same amount of leg? I am not on a feminist, anti-skirt rant here. I actually refused to wear pants at all for a stretch of time somewhere around kindergarten. This is a social-anthropological thesis question. If my hair, make-up, body type and generic fashion sense are all unchanged, why does a skirt make everyone say, "You look pretty today"?
Again, this is not a rant. And, apologies, it's also not particularly funny. But it is something that has nagged at the back of my mind and I wanted to put it out into the cosmos. Meanwhile, my knees are cold.