Guys + miniskirts = Confusion?

From reading stuff posted here, and every day life, it seems guys love girls in miniskirts, and will look ogle them. Yet, at my school dances, I see attractive girls wearing super mini skirts and tight tank tops, and guys walk by them, and don't care, or flinch, or notice them, or even look at them. It's weird... these girls are attractive. It seems to me that because girls dress so slutty now, guys have become somewhat desensitized to skimpy dress. Is this true?? or are those guys I mentioned just weird exceptions??